保证AC

#include <bits/stdc++.h>
using namespace std;
int main(){
	int a, cnt = 0;
	cin >> a;
	for (int i = 0; i <= a / 7; ++i){
		int j = (a - 7 * i) / 4;
		if ((a - 7 * i) % 4 == 0 && (a - i - j) % 3 == 0){
			cnt++;
        }
	}
	cout << cnt;
}