题解 | #挑7#

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

int main() {
    int n;
    while (cin >> n) {
        int res = 0;
        for (int i = 1; i <= n; ++i) {
            if (i % 7 == 0) {
                ++res;
                continue;
            } else {
                string str = to_string(i);
                for (auto j : str) {
                    if (j == '7') {
                        ++res;
                        break;
                    }
                }
            }
        }
        cout << res << endl;
    }
    return 0;
}