题解

#include<bits/stdc++.h>
using namespace std;
string s;
int n,m,n1;
int main(){
    cin>>s;
    for(int i=0;i<s.size()&&s[i]!='@';i++){
        if(s[i]=='('){n++;n1++;}
        if(s[i]==')'&&n1>=1){m++;n1--;}
        else if(s[i]==')'){
            cout<<"NO";
            return 0;
        }
    }
    if(n==m)cout<<"YES";
    else cout<<"NO";
    return 0;
}