P176 test 6-1 UVa673

//P176 test 6-1
#include<cstdio>
#include<stack>
#include<string>
#include<iostream>
using namespace std;

int main(){
    freopen("p.txt","r",stdin);
    freopen("pout.txt","w",stdout);
    string s;
    while( cin >> s){
        stack<char> t;
        if(s.empty()){
            printf("YES\n");
            continue;
        }
        ; i < s.size();i++){
            switch(s[i]){
                case '[':t.push(s[i]);break;
                case '(':t.push(s[i]);break;
                case ']':if(t.top() == '[')t.pop();else t.push(s[i]);break;
                case ')':if(t.top() == '(')t.pop();else t.push(s[i]);break;
                default :break;
            }
        }
        if(t.empty())printf("YES\n");
        else printf("NO\n");
    }
}