#include <bits/stdc++.h>

using namespace std;

char s[1010];
map<char, char> mp;

int main()
{
    mp['<'] = '>';
    mp['('] = ')';
    mp['{'] = '}';
    mp['['] = ']';
    
	while(cin >> s)
	{
		stack<char> st;
		for(int i = 0; i < strlen(s); i++)
		{
			if(st.empty()) st.push(s[i]);
			else
			{
				char cur = st.top();
				if(s[i] == mp[cur])
					st.pop();
				else st.push(s[i]);
			}
		}
		if(st.empty()) cout << "yes" << endl;
		else cout << "no" << endl;
	}
	return 0;
}