diff --git a/logs/2025-09.md b/logs/2025-09.md
index 921e3d0..9f4c178 100644
--- a/logs/2025-09.md
+++ b/logs/2025-09.md
@@ -6,9 +6,10 @@
 | 日期 | 題目 | 難度 | 語言 | 耗時 | 狀態 | 心得 |
 |------|------|------|------|------|------|------|
 | 09/01 | Maximum Average Pass Ratio | Medium | C# | 1hr | Done | 第一次用到Priority Queue |
-| 09/02 | Find The Number of Ways to Place People I | Medium | C# | 0.5hr | Done | 二維點位判斷 |
-| 09/02 | Find The Number of Ways to Place People I | Medium | go | 0.2hr | Done | go Prictice |
+| 09/02 | Find The Number of Ways to Place People I | Medium | C#, go | 0.7hr | Done | 二維點位判斷 |
 | 09/03 | Find The Number of Ways to Place People II | Hard | C# | 0.2hr | Done | Same as [#3025] |
+| 09/04 | Find Closest Person | Easy | C#, go | 0.1hr | Done | 數學判斷 |
+
 
 ### Week 2  
 | 日期 | 題目 | 難度 | 語言 | 耗時 | 狀態 | 心得 |
@@ -28,13 +29,13 @@
 ## 📈 本月統計
 
 ### 完成情況
-- **總練習天數**: 3 天
-- **完成題數**: 3題
-- **語言分布**: C# 3(題), Go 1(題)
-- **難度分布**: Easy 0(題), Medium 2(題), Hard 1(題)
+- **總練習天數**: 4 天
+- **完成題數**: 4題
+- **語言分布**: C# 4(題), Go 2(題)
+- **難度分布**: Easy 1(題), Medium 2(題), Hard 1(題)
 
 ### 時間投入
-- **總時間**: 1.9小時
+- **總時間**: 2小時
 - **平均每題**: 分鐘
 - **每日平均**: 分鐘
 
diff --git a/problems/3516-find-closest-person/README.md b/problems/3516-find-closest-person/README.md
new file mode 100644
index 0000000..3080eb1
--- /dev/null
+++ b/problems/3516-find-closest-person/README.md
@@ -0,0 +1,70 @@
+# [3516] Find Closest Person
+
+## 題目資訊
+- **難度**: Easy
+- **標籤**: Math
+- **題目連結**: [LeetCode](https://leetcode.com/problems/find-closest-person/)
+- **練習日期**: 2025-09-04
+
+## 題目描述
+You are given three integers `x`, `y`, and `z`, representing the positions of three people on a number line:
+
+`x` is the position of Person 1.
+`y` is the position of Person 2.
+`z` is the position of Person 3, who does **not** move.
+Both Person 1 and Person 2 move toward Person 3 at the same speed.
+
+Determine which person reaches Person 3 first:
+
+Return 1 if Person 1 arrives first.
+Return 2 if Person 2 arrives first.
+Return 0 if both arrive at the same time.
+Return the result accordingly.
+
+## 解題思路
+
+### 初步分析
+- 這題主要考察什麼概念？
+   距離計算和比較。使用絕對值計算兩點間距離
+- 有什麼關鍵限制條件？
+   比較兩個距離的大小關係
+- 預期時間/空間複雜度？
+   時間 O(1)，空間 O(1) - 只需要常數時間的計算
+
+### 解法概述
+**解法**: 
+   - 思路：
+      分別計算 Person 1 和 Person 2 到 Person 3 的距離，直接比較大小
+   - 時間複雜度：O(1)
+   - 空間複雜度：O(1)
+
+## 測試案例
+
+### 範例輸入輸出
+```
+Input: x = 2, y = 7, z = 4
+Output: 1
+Explanation: 
+- Person 1 is at position 2 and can reach Person 3 (at position 4) in 2 steps.
+- Person 2 is at position 7 and can reach Person 3 in 3 steps.
+Since Person 1 reaches Person 3 first, the output is 1.
+```
+
+### 邊界情況
+`1 <= x, y, z <= 100`
+
+## 學習筆記
+
+### 今天學到什麼？
+- 稍微練習了一下go func
+
+### 遇到的困難
+- 無
+
+### 改善方向
+- 無
+
+### 相關題目
+
+---
+**總結**: 今天這題考弱智?
diff --git a/problems/3516-find-closest-person/csharp/Program.cs b/problems/3516-find-closest-person/csharp/Program.cs
new file mode 100644
index 0000000..bb71b41
--- /dev/null
+++ b/problems/3516-find-closest-person/csharp/Program.cs
@@ -0,0 +1,60 @@
+// LeetCode 3516: Find Closest Person
+// 難度: Easy
+// 日期: 2025-09-04
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+public class Solution {
+    public int FindClosest(int x, int y, int z)
+    {
+        var distanceX = Math.Abs(x - z);
+        var distanceY = Math.Abs(y - z);
+
+        return distanceX == distanceY ? 0 : distanceX > distanceY ? 2 : 1;
+    }
+}
+
+// 測試程式
+public class Program
+{
+    public static void Main()
+    {
+        TestCase1();
+        TestCase2();
+        TestCase3();
+    }
+
+    // 基本測試案例 - Example 1
+    static void TestCase1()
+    {
+        var solution = new Solution();
+        // Input: x = 2, y = 7, z = 4
+        // Expected: 1 (Person 1 距離較近: |2-4| = 2 < |7-4| = 3)
+        var actual = solution.FindClosest(2, 7, 4);
+        var expected = 1;
+        Console.WriteLine($"Test 1: Input(2, 7, 4) Expected: {expected}, Actual: {actual}, Result: {(actual == expected ? "PASS" : "FAIL")}");
+    }
+
+    // 基本測試案例 - Example 2
+    static void TestCase2()
+    {
+        var solution = new Solution();
+        // Input: x = 2, y = 5, z = 6
+        // Expected: 2 (Person 2 距離較近: |5-6| = 1 < |2-6| = 4)
+        var actual = solution.FindClosest(2, 5, 6);
+        var expected = 2;
+        Console.WriteLine($"Test 2: Input(2, 5, 6) Expected: {expected}, Actual: {actual}, Result: {(actual == expected ? "PASS" : "FAIL")}");
+    }
+
+    // 基本測試案例 - Example 3
+    static void TestCase3() {
+        var solution = new Solution();
+        // Input: x = 1, y = 5, z = 3
+        // Expected: 0 (距離相等: |1-3| = 2 = |5-3| = 2)
+        var actual = solution.FindClosest(1, 5, 3);
+        var expected = 0;
+        Console.WriteLine($"Test 3: Input(1, 5, 3) Expected: {expected}, Actual: {actual}, Result: {(actual == expected ? "PASS" : "FAIL")}");
+    }
+}
diff --git a/problems/3516-find-closest-person/csharp/csharp.csproj b/problems/3516-find-closest-person/csharp/csharp.csproj
new file mode 100644
index 0000000..2150e37
--- /dev/null
+++ b/problems/3516-find-closest-person/csharp/csharp.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
diff --git a/problems/3516-find-closest-person/go/go.mod b/problems/3516-find-closest-person/go/go.mod
new file mode 100644
index 0000000..15d6b8c
--- /dev/null
+++ b/problems/3516-find-closest-person/go/go.mod
@@ -0,0 +1,3 @@
+module leetcode-3516
+
+go 1.18
diff --git a/problems/3516-find-closest-person/go/main.go b/problems/3516-find-closest-person/go/main.go
new file mode 100644
index 0000000..18a5e08
--- /dev/null
+++ b/problems/3516-find-closest-person/go/main.go
@@ -0,0 +1,71 @@
+// LeetCode 3516: Find Closest Person
+// 難度: Easy
+// 日期: 2025-09-04
+
+package main
+
+import "fmt"
+
+// TODO: 實作解法
+func findClosest(x, y, z int) int {
+    distanceX := abs(x - z)
+    distanceY := abs(y - z)
+
+    if distanceX == distanceY{
+        return 0
+    }else if distanceX > distanceY{
+        return 2
+    }else{
+        return 1
+    }
+}
+
+func abs(n int) int{
+    if n < 0 {
+        return -n
+    }
+    return n
+}
+
+func main() {
+    testCase1()
+    testCase2()
+    testCase3()
+}
+
+// 基本測試案例 - Example 1
+func testCase1() {
+    // Input: x = 2, y = 7, z = 4
+    // Expected: 1 (Person 1 距離較近: |2-4| = 2 < |7-4| = 3)
+    actual := findClosest(2, 7, 4)
+    expected := 1
+    fmt.Printf("Test 1: Input(2, 7, 4) Expected: %d, Actual: %d, Result: %s\n", 
+        expected, actual, getResult(actual == expected))
+}
+
+// 基本測試案例 - Example 2
+func testCase2() {
+    // Input: x = 2, y = 5, z = 6
+    // Expected: 2 (Person 2 距離較近: |5-6| = 1 < |2-6| = 4)
+    actual := findClosest(2, 5, 6)
+    expected := 2
+    fmt.Printf("Test 2: Input(2, 5, 6) Expected: %d, Actual: %d, Result: %s\n", 
+        expected, actual, getResult(actual == expected))
+}
+
+// 基本測試案例 - Example 3
+func testCase3() {
+    // Input: x = 1, y = 5, z = 3
+    // Expected: 0 (距離相等: |1-3| = 2 = |5-3| = 2)
+    actual := findClosest(1, 5, 3)
+    expected := 0
+    fmt.Printf("Test 3: Input(1, 5, 3) Expected: %d, Actual: %d, Result: %s\n", 
+        expected, actual, getResult(actual == expected))
+}
+
+func getResult(pass bool) string {
+    if pass {
+        return "PASS"
+    }
+    return "FAIL"
+}
\ No newline at end of file