[20260321] BOJ / G5 / 4와 7 / 이준희

Author: JHLEE325

JHLEE325/202603/21 BOJ G5 4와 7.md

@@ -0,0 +1,25 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int K = Integer.parseInt(br.readLine());
+
+        String binary = Integer.toBinaryString(K + 1);
+
+        StringBuilder sb = new StringBuilder();
+        for (int i = 1; i < binary.length(); i++) {
+            if (binary.charAt(i) == '0') {
+                sb.append('4');
+            } else {
+                sb.append('7');
+            }
+        }
+
+        System.out.println(sb.toString());
+    }
+}
+```