diff --git "a/lkhyun/202508/30 BOJ G4 \352\263\240\353\203\245\354\235\264.md" "b/lkhyun/202508/30 BOJ G4 \352\263\240\353\203\245\354\235\264.md"
new file mode 100644
index 00000000..35c7d3e0
--- /dev/null
+++ "b/lkhyun/202508/30 BOJ G4 \352\263\240\353\203\245\354\235\264.md"	
@@ -0,0 +1,42 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+    static int N;
+    static Map<Character,Integer> cur;
+
+    public static void main(String[] args) throws IOException {
+        N = Integer.parseInt(br.readLine());
+        String str = br.readLine();
+
+        cur = new HashMap<>();
+
+        int max = 0;
+        int ans = 0;
+        int left = 0, right = 0;
+
+        while(right < str.length()){
+            if(cur.size() < N || (cur.size() == N && cur.containsKey(str.charAt(right)))){
+               cur.put(str.charAt(right), cur.getOrDefault(str.charAt(right), 0)+1);
+               ans++;
+               right++;
+               max = Math.max(ans,max); 
+            }else{
+                ans--;
+                int temp = cur.get(str.charAt(left));
+                if(temp == 1){
+                    cur.remove(str.charAt(left++));
+                }else{
+                    cur.put(str.charAt(left++), temp-1);
+                }
+            }
+        }
+        bw.write(max+"");    
+        bw.close();
+    }
+}
+```