diff --git "a/lkhyun/202507/21 BOJ G4 \354\212\244\354\271\264\354\235\264\353\235\274\354\235\270 \354\211\254\354\232\264\352\261\260.md" "b/lkhyun/202507/21 BOJ G4 \354\212\244\354\271\264\354\235\264\353\235\274\354\235\270 \354\211\254\354\232\264\352\261\260.md"
new file mode 100644
index 00000000..fddbbc18
--- /dev/null
+++ "b/lkhyun/202507/21 BOJ G4 \354\212\244\354\271\264\354\235\264\353\235\274\354\235\270 \354\211\254\354\232\264\352\261\260.md"	
@@ -0,0 +1,35 @@
+```java
+import java.util.*;
+import java.io.*;
+
+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 int ans = 0;
+    public static void main(String[] args) throws Exception {
+        N = Integer.parseInt(br.readLine());
+
+        ArrayDeque<Integer> stk = new ArrayDeque<>();
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            int x = Integer.parseInt(st.nextToken());
+            int y = Integer.parseInt(st.nextToken());
+
+            while(!stk.isEmpty() && stk.peek() > y){
+                stk.pop();
+                ans++;
+            }
+            if(stk.isEmpty() && y > 0){
+                stk.push(y);
+            }else if(!stk.isEmpty() && stk.peek() < y){
+                stk.push(y);
+            }
+        }
+        ans += stk.size();
+        bw.write(ans + "\n");
+        bw.close();
+    }
+}
+```