[20250803] BOJ / G5 / 4와 7 / 김수연

Author: suyeun84

suyeun84/202508/03 BOJ G5 4와 7.md

@@ -0,0 +1,30 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class boj2877 {
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static StringTokenizer st;
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	static StringBuilder sb = new StringBuilder();
+
+	public static void main(String[] args) throws Exception {
+		nextLine();
+		int K = nextInt() + 1;
+		
+		int num = 0;
+        while(K != 0){
+            num = K % 2;
+            sb.append(num);
+            K = K / 2;
+        }
+        StringBuilder result = new StringBuilder();
+        for(int i = sb.toString().length() - 2; i >= 0; i--){
+            if(sb.charAt(i) == '0') result.append(4);
+            else result.append(7);
+        }
+        System.out.println(result.toString());
+	}
+}
+```