题解 | #挑7#

#include <iostream>
using namespace std;
//挑7

int main() {
    int n;
    cin >> n;
    int num = 0, temp;
    for (int i = 1; i <= n; i++) {
        if (i % 7 == 0) {
            num++;
        } else {
            temp = i;
            while (temp) {
                if (temp % 10 == 7) {
                    num++;
                    break;
                }
                temp = temp / 10;
            }
        }
    }
    cout << num;
    return 0;
}