https://www.luogu.com.cn/record/67427972

代码：

#include<bits/stdc++.h>

using namespace std;

int main(){
  char a = 0;
  int i = 0;
  cin >> a;
  while (a != "@"){
    cin >> a;
    if (a == "("){
      i++;
    }else if (a == ")"){
      i--;
    }
  }
  if (a == 0) {
    cout << "YES";
  }else{
    cout << "NO";
  }
  
  return 0;
}