diff --git "a/Seol-JY/202507/21 G4 \352\263\265\354\234\240\352\270\260 \354\204\244\354\271\230.md" "b/Seol-JY/202507/21 G4 \352\263\265\354\234\240\352\270\260 \354\204\244\354\271\230.md"
new file mode 100644
index 00000000..5765e611
--- /dev/null
+++ "b/Seol-JY/202507/21 G4 \352\263\265\354\234\240\352\270\260 \354\204\244\354\271\230.md"	
@@ -0,0 +1,53 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        
+        int N = Integer.parseInt(st.nextToken());
+        int C = Integer.parseInt(st.nextToken());
+        
+        int[] houses = new int[N];
+        for (int i = 0; i < N; i++) {
+            houses[i] = Integer.parseInt(br.readLine());
+        }
+        
+        Arrays.sort(houses);
+        
+        int left = 1;
+        int right = houses[N - 1] - houses[0];
+        int answer = 0;
+        
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            
+            if (canInstall(houses, C, mid)) {
+                answer = mid;
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+        
+        System.out.println(answer);
+    }
+    
+    private static boolean canInstall(int[] houses, int C, int distance) {
+        int count = 1;
+        int lastPos = houses[0];
+        
+        for (int i = 1; i < houses.length; i++) {
+            if (houses[i] - lastPos >= distance) {
+                count++;
+                lastPos = houses[i];
+                if (count >= C) return true;
+            }
+        }
+        
+        return false;
+    }
+}
+```