题解

#include <bits/stdc++.h>
#include <stack>
using namespace std;
stack<char>st;
int main()
{
	char s;
	while(cin>>s){
		if(s=='@') break;
		else if(s=='(') st.push(s);
		else if(s==')'){
			if(!st.empty()) st.pop();
			else{
				cout<<"NO";
				return 0;
			}
		}
	}
	if(!st.empty()) cout<<"NO";
	else cout<<"YES";
	return 0;
}