easy

自行学习

#include <iostream>
#include <string>

int main(){
    std::string s;
    std::cin >> s;
    int left = 0, right = 0;
    for(int i = 0; i < s.size(); i++){
        if (s[i] == '(') left++;
        else if (s[i] == ')') right++;
    }
    if (left == right) std::cout << "YES";
    else std::cout << "NO";
    return 0;
}