Go: package main

import (
	"bufio"
	"fmt"
	"os"
)

var sc = bufio.NewScanner(os.Stdin)

func nextString() string {
	sc.Scan()
	return sc.Text()
}

func main() {
	sc.Buffer(make([]byte, 0), 1000000009)

	for {
		var s string
		s = nextString()
		if s == "." {
			break
		}
		var st []byte
		is_valid := true

		for _, value := range s {
			if value == '(' {
				st = append(st, byte(value))
			}
			if value == '[' {
				st = append(st, byte(value))
			}
			if value == ')' {
				if len(st) == 0 || st[len(st)-1] != '(' {
					is_valid = false
					break
				} else {
					st = st[:len(st)-1]
				}
			}
			if value == ']' {
				if len(st) == 0 || st[len(st)-1] != '[' {
					is_valid = false
					break
				} else {
					st = st[:len(st)-1]
				}
			}
		}
		if len(st) != 0 {
			is_valid = false
		}
		if is_valid {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: //
//  main.cpp
//  The Balance of the World
//
//  Created by x15071xx on 2017/06/16.
//  Copyright ?? 2017??´ AIT. All rights reserved.
//

#include <iostream>
#include <vector>
#include <cstdio>
#include <string>
#include <cstdlib>
#include <string>
using namespace std;
int main(int argc, const char * argv[]) {
    
    
    while(1){
        string yn = "yes";
        string str;
        vector<char> st;
        getline(cin, str);
        
        
        if (str == ".") {
            break;
        }
        
        for (int i = 0;  i < str.size(); i++) {
            
            if (str[i] == '(' || str[i] == '[') {
                st.push_back(str[i]);
            }
            
            if (str[i] == ')') {
                
                
                if ('(' != st.back()) {
                    yn = "no";
                    break;
                }
                
                st.pop_back();
                
            }

            if (str[i] == ']') {
                
                if ('[' != st.back()) {
                    yn = "no";
                    break;
                }
                
                st.pop_back();
                
            }

        }
        
        if (!st.empty()) {
            yn = "no";
        }
        
        cout << yn << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <string>
using namespace std;
#define rep(i,n) for(int i = 0 ; i < n ; i++)



int main()
{
  string str;
  
  while(true){
    getline(cin, str);
    if(str[0] == '.') break;
    
    int len = 0;
    while(str[len] != '\0'){
      len++;
    }
        
    int cnt_1 = 0, cnt_2 = 0;
    for(int i = 0 ; i < len ; i++){
      if(str[i] == '('){
	cnt_1++;
      }
      if(str[i] == '['){
	cnt_2++;
      }
      if(str[i] == ')'){
	cnt_1--;
      }
      if(str[i] == ']'){
	cnt_2--;
      }
    }
    if(cnt_1 == cnt_2){
      cout << "yes" << '\n';
    }else{
      cout << "no" << '\n';
    }
  }
}

C++: #include<iostream>
#include<string>
#include<vector>

int main(){
	std::vector<std::string>Vstr;
	while(1){
		std::string str;
		char bef;
		int count=0;
		std::getline(std::cin,str);
		if(str==".")break;
		for(int i=0;i<str.size();i++){
			if(str[i]=='('||str[i]=='['){
				count++;
				bef=str[i];
			}else if(str[i]==')'||str[i]==']'){
				count--;
				if(!((str[i]==')'&&bef=='(')||(str[i]==']'&&bef=='['))){
					Vstr.push_back("no");
					goto end;
				}
			}
		}
		if(count==0)Vstr.push_back("yes");
		else Vstr.push_back("no");
		end:;
		std::cout<<std::endl;
	}
	for(int i=0;i<Vstr.size();i++)std::cout<<Vstr[i]<<std::endl;
	return 0;
}

C++: #include <bits/stdc++.h>
#define endl '\n'
#define int long long
#define lint long long
#define pii pair<int, int>
#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORR(i, a, b) for(int i = (a); i > (b); --i)
#define REP(i, n) FOR(i, 0, n)
#define SZ(v) ((int)v.size())
#define ZERO(a) memset(a, 0, sizeof(a))
#define MINUS(a) memset(a, 0xff, sizeof(a))
#define FILLINF(a) memset(a, 0x3f, sizeof(a))
#define POW(n) (1LL << (n))
#define POPCNT(n) (__builtin_popcount(n))
#define IN(i, a, b) ((a) <= (i) && (i) <= (b))
using namespace std;
template <typename T> inline bool CHMIN(T& a, T b) { if(a > b) { a = b; return 1; } return 0; }
template <typename T> inline bool CHMAX(T& a, T b) { if(a < b) { a = b; return 1; } return 0; }
template <typename T> inline void SORT(T& a) { sort(begin(a), end(a)); }
template <typename T> inline void REV(T& a) { reverse(begin(a), end(a)); }
template <typename T> inline void UNI(T& a) { sort(a.begin(), a.end()); a.erase(unique(a.begin(), a.end()), a.end()); }
template <typename S, typename T> inline T LB(S& v, T a) { return *lower_bound(begin(v), end(v), a); }
template <typename S, typename T> inline int LBP(S& v, T a) { return lower_bound(begin(v), end(v), a) - begin(v); }
template <typename S, typename T> inline T UB(S& v, T a) { return *upper_bound(begin(v), end(v), a); }
template <typename S, typename T> inline int UBP(S& v, T a) { return upper_bound(begin(v), end(v), a) - begin(v); }
template <typename S, typename T> ostream& operator << (ostream& os, const pair<S, T>& p) { os << p.first << " " << p.second; return os; }
template <typename S, typename T> istream& operator >> (istream& is, pair<S, T>& p) { is >> p.first >> p.second; return is; }
template <typename T> ostream& operator << (ostream& os, const vector<T>& v) { for (int i = 0; i < v.size(); ++i) { if (i) os << " "; os << v[i]; } return os; }
template <typename T> istream& operator >> (istream& is, vector<T>& v) { for(T& in : v) is >> in; return is; }
template <typename T = int> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...)); }
template <typename T, typename V> typename enable_if<is_class<T>::value == 0>::type fill_v(T& t, const V& v) { t = v; }
template <typename T, typename V> typename enable_if<is_class<T>::value != 0>::type fill_v(T& t, const V& v) { for(auto &e : t) fill_v(e, v); }
const double PI = 3.14159265358979323846;
const double EPS = 1e-10;
const lint INF = 0x3f3f3f3f3f3f3f3f;
const lint MOD = 1000000007;

void _main() {
    string s;
    while (getline(cin, s), s != ".") {
        stack<char> st;
        bool no = false;
        REP (i, s.size()) {
            if (s[i] == '(' || s[i] == '[') st.push(s[i]);
            else if (s[i] == ')') {
                if (st.empty() || st.top() != '(') {
                    no = true;
                    break;
                }
                st.pop();
            } else if (s[i] == ']') {
                if (st.empty() || st.top() != '[') {
                    no = true;
                    break;
                }
                st.pop();
            }
        }
        if (!st.empty()) no = true;
        cout << (no ? "no" : "yes") << endl;
    }
}

signed main(signed argc, char **argv) {
    if (argc > 1) {
        if (strchr(argv[1], 'i')) freopen("input.txt", "r", stdin);
        if (strchr(argv[1], 'o')) freopen("output.txt", "w", stdout);
    }
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(10);
    _main();
    return 0;
}