백준 1526번

원본 : https://www.acmicpc.net/problem/1526

1526번: 가장 큰 금민수

 

풀이

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
    private static final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws Exception {
        int n = Integer.parseInt(bufferedReader.readLine());

        while (true) {
            String str = String.valueOf(n);
            int cnt = 0;

            for (char ch : str.toCharArray()) {
                if (ch == '4' || ch == '7') {
                    cnt++;
                }
            }

            if (cnt == str.length()) {
                System.out.println(n);
                break;
            }

            n--;
        }
    }
}