#include <iostream>
#include <string>
using namespace std;

bool correcto(const string sec, int& n, int& p, int& c) {
    if (n == sec.size()) {
        if (p != 0 or c != 0) return false;
        return true;
    }
    if (sec[n] == '(') correcto(sec,n+1,p+1,c);
    else if (sec[n] == '[') correcto(sec,n+1,p,c+1);
    else if (sec[n] == ')') correcto(sec,n+1,p-1,c);
    else if (sec[n] == ']') correcto(sec,n+1,p,c-1);
}

int main () {
    string sec;
    while (cin >> sec) {
        int n=0, p=0, c=0;
        if (correcto(sec, n, p, c)) cout << "si" << endl;
        else cout << "no" << endl;
    }
}