题解 | #挑7#

#include <stdio.h>

int main() {
    int n;
    int count = 0;
    scanf("%d", &n);
    if (n < 7) {
        count = 0;
    } else {
        for (int i = 7; i <= n; i++) {
            if(i%7 == 0)
            {
                count++;
            }
            else{
                int k = i;
                while (k!=0) {

                    if(k%10 == 7)
                    {
                        count++;
                        break;
                    } 
                    k/=10;               
                }
            }
               
            
        }
    }
    printf("%d",count);
}