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 <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <stack>
#include <cstdio>
#define rep(i, j) for(int i = 0; i < j; i++)
#define all(i) i.begin(), i.end()
using namespace std;
int main()
{
	while (1)
	{
		int id = 0;
		stack<int> stck;
		string str; getline(cin, str);
		if (str[0] == '.') { break; }
		rep(i, (int)str.size() + 1)
		{
			switch (str[i])
			{
			case '(':	stck.push(1);	break;
			case '[': stck.push(2); break;
			case ')': 
				if (stck.size() == 0) { id = 1; }
				else if (stck.top() == 1) { stck.pop(); }
				else { id = 1; } break;
			case ']': 
				if (stck.size() == 0) { id = 1; }
				else if (stck.top() == 2) { stck.pop(); }
				else { id = 1; } break;
			}
		}
		if (id == 1) { printf("no\n"); }
		else { printf("yes\n"); }
	}
	return 0;
}

C++: 
#include<iostream>
#include<stack>
main(){
  for(char i,f,c,s[101];fgets(s,101,stdin),s[0]-'.';){
 std::stack<char> t;
 for(f=i=0;c=s[i++],c!='\n';){
  if(c==40|c==91)t.push(c);
  if(c==41|c==93){
   if(t.size()&&c-t.top()<3)t.pop();
   else f=1;
  }
 }
 puts(f&t.size()?"no":"yes");
}}

C++: #define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for(int i=0; i<(n); ++i)
#define FOR(i, m, n) for(int i=(m); i<(n); ++i)
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define mp make_pair
#define pb push_back
#define dump(x) cerr << #x << " = " << (x) << endl;
#define qp(f) [](auto i){return f;}
using LL=long long;
using VI=vector<int>;
using VL=vector<LL>;
using VS=vector<string>;
using VVI=vector<vector<int>>;
using PII=pair<int, int>;
const int inf = (int)1e9;
const LL MOD = 1000000007;
const double pi = acos(-1.0);
template<class T>T Sort(T & a) { sort(a.begin(), a.end()); return a; }
template<class T>T ReSort(T& a) { sort(a.rbegin(), a.rend()); return a; }
template<class T>T Reverse(T& a) { reverse(a.begin(), a.end()); return a; }
template<class T>void Unique(T& a) { a.erase(unique(a.begin(), a.end()), a.end()); }
template<class T>auto Max(T a) { return *max_element(a.begin(), a.end()); }
template<class T>auto Min(T a) { return *min_element(a.begin(), a.end()); }
template<class T, class U>int Count(T a, U c) { return count(a.begin(), a.end(), c); }
template<class T, class U>U Sum(T a, U init = 0) { return accumulate(a.begin(), a.end(), init); }
template<class T>T Age(T a, T b) { return (a + b - 1) / b; }
template<class T>T gcd(T n, T m) { return m == 0 ? n : gcd(m, n % m); }
template<class T>T lcm(T n, T m) { return n / gcd(n, m) * m; }
string Snum = "0123456789";

/* INPUT */
struct inputter_Str {
	vector<string> inputbuffer;
	string operator [](int n) { while (inputbuffer.size() <= n) { string s; cin >> s; inputbuffer.push_back(s); }return inputbuffer[n]; }
	operator string() { string s; cin >> s; inputbuffer.push_back(s); return s; }
}in;
struct inputter_Int {
	int operator [](int n) { return stoi(in[n]); }
	operator int() { return stoi(string(in)); }
}ini;
struct inputter_LL {
	LL operator [](int n) { return stoll(in[n]); }
	operator LL() { return stoll(string(in)); }
}inl;
struct inputter_Double {
	double operator [](int n) { return stod(in[n]); }
	operator double() { return stold(string(in)); }
}ind;
VI invi(int n, int m) { VI v(m); for (int i = 0; i < m; ++i)v[i] = ini[n + i]; return v; }
VL invl(int n, int m) { VL v(m); for (int i = 0; i < m; ++i)v[i] = inl[n + i]; return v; }
int Suminvi(int n, int m) { return Sum(invi(n, m), 0); }LL Suminvl(int n, int m) { return Sum(invl(n, m), 0LL); }
int Maxinvi(int n, int m) { return  Max(invi(n, m)); }LL Maxinvl(int n, int m) { return Max(invl(n, m)); }
int Mininvi(int n, int m) { return  Min(invi(n, m)); }LL Mininvl(int n, int m) { return Min(invl(n, m)); }

/* OUTPUT */
struct boolswitch { string t, f; boolswitch(string tr, string fa) :t(tr), f(fa) {} }yes("yes", "no"), Yes("Yes", "No"), YES("YES", "NO"), Yay("Yay!", ":(");
struct divizer { string s; divizer(string s_) :s(s_) {} }spc(" "), nosp("");
struct outputter {
	bool flag = false; boolswitch bs; divizer di;
	outputter(bool f, boolswitch b, divizer d) :flag(f), bs(b), di(d) {}
	template<class T>outputter operator ,(T o) {
		if (flag)cout << di.s; cout << o;
		outputter t(true, bs, di); return t;
	}
	outputter operator ,(double o) {
		if (flag)cout << di.s; printf("%.20f", o);
		outputter t(true, bs, di); return t;
	}
	outputter operator ,(bool o) {
		if (flag)cout << di.s; cout << (o ? bs.t : bs.f);
		outputter t(true, bs, di); return t;
	}
	template<class T> outputter operator ,(vector<T> o) {
		if (flag)cout << di.s;
		for (int i = 0; i < (int)o.size(); ++i)cout << o[i] << (i == (int)o.size() - 1 ? "" : di.s);
		outputter t(true, bs, di); return t;
	}
	template<class T, class U> outputter operator ,(pair<T, U> o) {
		if (flag)cout << di.s;
		cout << "[" << o.first, ", " << o.second << "]";
		outputter t(true, bs, di); return t;
	}
	outputter operator ,(outputter o) { cout << '\n'; return o; }
	outputter operator ,(boolswitch b) { outputter t(flag, b, di); return t; }
	outputter operator ,(divizer d) { outputter t(flag, bs, d); return t; }
}out(false, Yes, spc);

/* ANSWER */
struct Answer {
	int mini = INT_MAX, maxi = INT_MIN, sumi = 0;
	LL minl = LLONG_MAX, maxl = LLONG_MIN, suml = 0LL;
	double mind = DBL_MAX, maxd = DBL_MIN, sumd = 0.;
	int count = 0;
	void operator =(int n) { mini = min(mini, n); maxi = max(maxi, n); sumi += n; count++; }
	void operator =(LL n) { minl = min(minl, n); maxl = max(maxl, n); suml += n; count++; }
	void operator =(double n) { mind = min(mind, n); maxd = max(maxd, n); sumd += n; count++; }
}ans;

string re(string s) {
	string ret = "";
	for (auto c : s) {
		if (c == '[' || c == ']' || c == '(' || c == ')')ret += c;
	}
	return ret;
}

bool solve(string s) {
	bool ret = true;
	int l = sz(s);
	while (!s.empty()) {
		rep(i, sz(s) - 1) {
			if ((s[i] == '(' && s[i + 1] == ')') || (s[i] == '[' && s[i + 1] == ']')) {
				s.erase(i, 2);
				i--;
			}
		}
		if (l == sz(s)) { ret = false; break; }
		l = sz(s);
	}
	return ret;
}

int main() {
	string s;
	while (getline(cin, s) && s != ".") {
		out, yes, solve(re(s)), out;
	}
}

C++: #include <iostream>
#include <stack>
#include <vector>
using namespace std;


int main(){
	string str;
	while(getline(cin,str)&& str!="."){
		string z;
		for(int i=0;i<str.size();i++)
			if(str[i]=='(' || str[i]==')' || str[i]=='[' || str[i]==']')
				z+=str[i];
		stack<char> s;
		bool f=true;
		for(int i=0;i<z.length();i++){
			if(z.empty() || z[i] == '(' || z[i] == '[')
				s.push(z[i]);
			else if( (s.top() == '(' && z[i] == ')') || (s.top() == '[' && z[i] == ']') )
				s.pop();
			else{
				f=false;
				break;
			}
		}
		cout << (f && s.empty()?"yes":"no") << endl;
	}
}