题解 | #挑7#

#include <stdio.h>
#include <string.h>

int main(){

    int n;
    scanf("%d", &n);

    int count = 0;
    for(int i = 1, k = 0; i <= n; i++){
        if(i % 7 == 0){
            count++;
            continue;;
        }
        int tmp;
        k = i;
        while(k != 0){
            tmp = k % 10;
            if(tmp == 7){
                count++;
                break;
            }
            k = k / 10;
        }
    }

    printf("%d", count);


    return 0;
}