华为机试：挑7

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        if (i % 7 == 0) {
            ans++;
        }
        else {
            string str = to_string(i);
            if (find(str.begin(), str.end(), '7') != str.end()) {
                ans++;
            }
        }
    }
    cout << ans << endl;
    return 0;
}