#include<bits/stdc++.h>
int main()
{
	std::string s;std::getline(std::cin,s);
	int lens,ans=0,left=0;
	lens=s.size()-1;
	for(int i=0;i<=lens;i++)
	{
		if(s[i]=='(')left++;
		if(s[i]==')')
		{
			if(left)left--;
			else {ans++;left++;}
		}
	}
	if(left)ans+=left/2;
	std::cout<<ans;
	return 0;
}