#include <iostream>
using namespace std;

int main(){
    int len,res=0;
    char x1,x2;
    cin>>len>>x1>>x2;
    for(int i=0;i<(len-2);i++){
        x1=x2;
        cin>>x2;
        if((x1=='(' && x2==')') || (x1==')' && x2==')')){
            res++;
        }
    }
    cout<<res<<endl;
    return 0;
}