题解 | #挑7#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            int b = 0;
            for (int i = 7 ; i <= a; i ++ ) {
                if ((i % 7 == 0)||((i - 7) % 10 == 0)||(i / 10 == 7)) {
                    b++;
                    continue;
                }  
                int res = i;
                while (res > 10) {
                    if ((res / 10) == 7 || (res - 7) % 10 == 0) {
                        b++;
                        break;
                    }
                    res /= 10;
                }
            }
            System.out.println( b);
        }
    }
}