题解 | #挑7#

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

int main() {
    string str;
    int num,cnt = 0;
    cin >> num;
    for (int i = 7; i <= num; ++i)
    {
        if (i % 7 == 0)
        {
            cnt++;
            continue;
        }
        str = to_string(i);
        for (char x : str)
        {
            if (x == '7')
            {
                cnt++;
                break;
            }
        }
    }
    cout << cnt << endl;
    return 0;
}