题解 | #挑7#

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    int ans = 0;
    int temp;
    for (int i = 1; i <= n; i++) {
        temp = i;
        if (temp % 7 == 0) {
            ans++;
        } 
        else {
            while (temp > 0) {
                if (temp % 10 == 7) {
                    ans++;
                    break;
                } else temp = temp / 10;
            }
        }
    }
    cout << ans << endl;
    return 0;
}
// 64 位输出请用 printf("%lld")