70pts求条(难道是不用栈就会被针对吗)

#include<bits/stdc++.h>
using namespace std;
string s;
int f=0;
int main(){
	cin >> s;
	for(int i = 0;i < s.size(); i++){
		if(s[i] == '(') f++;
		else if(s[i] == ')') f--;
		else if(s[i] == ')'&&f<=0){
			cout << "NO";
			return 0;
		}
	}
	if(f!=0) cout << "NO";
	else cout << "YES";
	return 0;
}