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++: // includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
#define bit(n) (1LL<<(n))
#define INT(n) int n; cin >> n;
#define LL(n) ll n; cin >> n;
#define DOUBLE(n) double n; cin >> n;
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
typedef complex<double> cd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}


int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(20);
  while(true){
  	bool ok = false;
  	bool res = true;
  	char c;
  	stack<char> st;
  	while(true){
  		scanf("%c", &c);
  		if(c == '.' && !ok && st.size() == 0)return 0;
  		if(c == '.'){
  			if(res && st.size() == 0)printf("yes\n");
  			else printf("no\n");
  			break;
  		}else{
  			if(c != '\n')ok = true;
  			if(c == '(' || c == '[')st.push(c);
  			else if(c == ')'){
  				if(!sz(st))res = false;
  				else {
  					char d = st.top(); st.pop();
  					if(d != '(')res = false;
  				}
  			} else if(c == ']'){
  				if(!sz(st))res = false;
  				else {
  					char d = st.top(); st.pop();
  					if(d != '[')res = false;
  				}
  			}
  		}
  	}
  }
  return 0;
}

C++: #include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<cmath>
#include<climits>
#include<ctime>
#include<cstring>
#include<stack>
#include<queue>

#define ALL(v) (v).begin(),(v).end()
#define REP(i,p,n) for(int i=p;i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define DUMP(list) cout << "{ "; for(auto nth : list){ cout << nth << " "; } cout << "}" << endl;


using namespace std;



int main()
{

  while(true){
    string text;
    getline(cin,text);

    if(text=="."){
      break;
    }

    stack<char> kakko;
    bool flag=true;

    for(int i=0;i<text.length();i++){
      
      //cout << text[i] << endl;
      
      if(text[i]=='('||text[i]=='['){
        kakko.push(text[i]);
      }


      if(text[i]==')'||text[i]==']'){
       if(kakko.empty()){
          flag = false;
          break; 
        }else if((kakko.top()=='(' && text[i]==']')||((kakko.top()=='[' && text[i]==')'))){
          flag = false;
          break;
        }else{
          kakko.pop();
        }
      }

    }
    
    if(!kakko.empty()){
      flag = false;
    }
    
    if(flag){
      cout << "yes" << endl;
    }else{
      cout << "no" << endl;
    }

  }

  return 0;
}

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

using std::cin;
using std::cout;
using std::endl;

int main(void) {
	std::string str;
	getline(cin, str);

	while (str[0] != '.' && str.length() != 0) {
		std::stack<int> check;
		bool much = true;
		for (int i = 0; i < str.length()+1; i++) {
			if (much) {
				if (str[i] == '(') {
					check.push(1);
				}
				if (str[i] == ')') {
					if (check.empty()) {
						much = false;
					} else {
						if (check.top()!=1) {
							much = false;
						}
						check.pop();
					}
				}
				if (str[i] == '[') {
					check.push(2);
				}
				if (str[i] == ']') {
					if (check.empty()) {
						much = false;
					} else {
						if (check.top()!=2) {
							much = false;
						}
						check.pop();
					}
				}
			}
		}
		if (much && check.empty()) {
			cout << "yes" << endl;
		} else {
			cout << "no" << endl;
		}
		getline(cin, str);
	}

	return 0;
}