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

char allowedBrackets[] { '(', ')', '{', '}', '[', ']', '<', '>' };

bool isOpenBracket(char c)
{
	for (int i = 0; i < sizeof(allowedBrackets) / sizeof(allowedBrackets[0]); i+=2)
		if (c == allowedBrackets[i])
			return true;

	return false;
}

bool isCloseBracket(char c)
{
	for (int i = 1; i < sizeof(allowedBrackets) / sizeof(allowedBrackets[0]); i += 2)
		if (c == allowedBrackets[i])
			return true;

	return false;
}

int main()
{
	string s;
	cin >> s;


	stack<char> st;

	for (int i = 0; i < s.length(); i++)
	{
		if (isOpenBracket(s[i]))
		{
			st.push(s[i]);
		}

		if (isCloseBracket(s[i]))
		{
			st.pop();
		}
	}

	return 0;
}