#include <iostream>
#include <string>
#include <queue>
using std::string;

struct stack
{
    std::queue<char> q1, q2;
    int curr_size;
    stack()
    {
        curr_size = 0;
    }
    void push(char x)
    {
        q1.push(x);
        curr_size++;
    }
    void pop()
    {
        if (q1.empty())
            return;
        while (q1.size() != 1)
        {
            q2.push(q1.front());
            q1.pop();
        }
        q1.pop();
        curr_size--;
        std::queue<char> q = q1;
        q1 = q2;
        q2 = q;
    }
    int top()
    {
        if (q1.empty())
            return -1;

        while (q1.size() != 1) {
            q2.push(q1.front());
            q1.pop();
        }
        char temp = q1.front();
        q1.pop();
        q2.push(temp);
        std::queue<char> q;
        q = q1;
        q1 = q2;
        q2 = q;
        return temp;
    }
    int size()
    {
        return curr_size;
    }
    bool empty()
    {
        return curr_size == 0;
    }
};

int anterior(char s)
{
    if (s == '(' || s == ')')
        return 1;
    else if (s == '[' || s == ']')
        return 2;
    else if (s == '{' || s == '}')
        return 3;
}
bool verificare(std::string s,stack Stack)
{

    for (int i = 0; i < s.size(); i++)
    {


        if (s[i] == '{' || s[i] == '[' || s[i] == '(')
        {
            Stack.push(s[i]);
            if (anterior(Stack.top()) <= anterior(s[i])) return false;


        }
        else if (s[i] == '}' || s[i] == ']' || s[i] == ')')
        {
            if (anterior(s[i]) != anterior(Stack.top())) return false;
            Stack.pop();

        }
    }
    if (Stack.size() != 0)
        return false;

    return true;
}
int main()
{
    string s;
    std::cin >> s;
    stack Stack;
    if (verificare(s,Stack))
    {
        std::cout << "Expresia este valida.\n";
    }
    else
    {
        std::cout << "Expresia nu este valida.\n";
    }
    return 0;
}