4949.cpp

// Authored by : BaaaaaaaaaaarkingDog
// Co-authored by : -
// http://boj.kr/9dd230a7a6cf4fdaa3f2abde6c96c59c
#include <bits/stdc++.h>
using namespace std;

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  while(true){
    string a;
    getline(cin, a);
    if(a == ".") break;
    stack<char> s;
    bool isValid = true;
    for(auto c : a){
      if(c == '(' || c == '[') s.push(c);
      else if(c == ')'){
        if(s.empty() || s.top() != '('){
          isValid = false;
          break;
        }
        s.pop();
      }
      else if(c == ']'){
        if(s.empty() || s.top() != '['){
          isValid = false;
          break;
        }
        s.pop();
      }
    }
    if(!s.empty()) isValid = false;
    if(isValid) cout << "yes\n";
    else cout << "no\n";
  }
}