简单

#include <iostream>
#include <stack>
#include <string>
using namespace std;

bool is_matching_pair(char left, char right) {
    return (left == '(' && right == ')') || (left == '[' && right == ']');
}

bool is_balanced(string expr) {
    stack<char> s;
    for (char c : expr) {
        if (c == '@') break;  
        
        if (c == '(' || c == '[') {
            s.push(c);  
        } else if (c == ')' || c == ']') {
            if (s.empty()) {
                return false;  
            }
            char top = s.top();
            s.pop();
            if (!is_matching_pair(top, c)) {
                return false;  
            }
        }
    }
    return s.empty();  
}

int main() {
    string expr;
    getline(cin, expr);
    
    if (is_balanced(expr)) {
        cout << "YES" << endl;
    } else {
        cout << "NO" << endl;
    }
    
    return 0;
}