#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;
}