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++: #include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;
using PII = pair<ll, ll>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\n'; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

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 (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<'\n'
#define p2(s, t) cout << (s) << " " << (t) << '\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\n'
#define p_yes() p("yes")
#define p_no() p("no")
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())
#define MP make_pair

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);

bool kakko(char c){
  if(c=='(' || c==')' || c=='[' || c==']'){
    return true;
  }else{
    return false;
  }
}

bool check(string s){
  stack<char> st;
  for(char c : s){
    if(!kakko(c)) continue;
    if(c=='('){
      st.push(c);
    }

    else if(c==')'){
      if(st.size()==0){
        return false;
      }
      else{
        if(st.top()=='('){
          st.pop();
        }
        else{
          // [ or ] or )
          return false;
        }
      }
    }

    else if(c=='['){
      st.push(c);
    }

    else if(c==']'){
      if(st.size()==0){
        return false;
      }
      else{
        if(st.top()=='['){
          st.pop();
        }
        else{
          return false;
        }
      }
    }
  }
  return st.size()==0;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    string s;

    while(getline(cin, s)){
      if(s==".") return 0;

      if(check(s)){
        p_yes();
      }else{
        p_no();
      }
    }
    
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int main(void){
    string str,ans=")]";
    while(getline(cin,str)&&str!="."){
        stack<int> sta;
        for(int i=0;i<str.size();i++){
            if(str[i]=='(')sta.push(0);
            if(str[i]=='[')sta.push(1);
            if((str[i]==')'||str[i]==']')&&!sta.empty()&&str[i]==ans[sta.top()])sta.pop();
        }
        if(sta.empty())cout<<"yes\n";
        else cout<<"no\n";
    }
}

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

using namespace std;

int main( void )
{
	string in;
	char stack[101];
	while(getline(cin, in), in[0] != '.') {
		int pointer = 0;
		bool hit = true;
		int len = in.size();
		for(int i=0; i < len; ++i) {
			if(in[i] == '(' || in[i] == '[') {
				stack[pointer++] = in[i];
			}
			else if(in[i] == ')') {
				if(!pointer || '(' != stack[--pointer]) hit = false;
			}
			else if(in[i] == ']') {
				if(!pointer || '[' != stack[--pointer]) hit = false;
			}
		}
		if(!pointer && hit)
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
}

C++: #include <iostream>
#include <iomanip>
#include <sstream>
#include <stdio.h>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <math.h>
#include <utility>
#include <string>
#include <ctype.h>
#include <cstring>
#include <cstdio>
#include <sstream>
#include <functional>

using namespace std;

#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define INF 114514810
#define ll long long
#define scanf scanf_s

string s;

int main()
{
	while (getline(cin, s))
	{
		if (s[0] == '.') break;
		vector<char> v;
		REP(i,105)v.push_back('0');
		bool f = true;
		REP(i, s.size())
		{
			if (s[i] == '[') v.push_back('[');
			if (s[i] == '(') v.push_back('(');
			if (s[i] == ']')
			{
				if (v.back() == '[')
				{
					v.pop_back();
				}
				else f = false;
			}
			if (s[i] == ')')
			{
				if (v.back() == '(')
				{
					v.pop_back();
				}
				else f = false;
			}
		}
		if (f&&v.back()=='0') cout << "yes" << endl;
		else cout << "no" << endl;
	}
	return 0;
}

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

using namespace std;

bool ok (string s)
{
    stack<char> stk;
    for (int i=0; i<s.size(); i++)
    {
        if (s[i]=='(') stk.push('(');
        if (s[i]=='[') stk.push('[');
        if (s[i]==')')
        {
            if (stk.empty()) return false;
            else if (stk.top()!='(') return false;
            else stk.pop();
        }
        if (s[i]==']')
        {
            if (stk.empty()) return false;
            else if (stk.top()!='[') return false;
            else stk.pop();
        }
    }
    return true;
}

int main()
{
    vector<bool> f;
    string t;
    while (1)
    {
        getline(cin, t);
        if (t==".") break;
        f.push_back(ok(t));
    }
    for (int i=0; i<f.size(); i++) cout<<(f[i]? "yes\n" : "no\n");
    return 0;
}