#include<bits/stdc++.h>
int main(){
    int n,k;std::cin>>n>>k;k--;
    std::string s;std::cin>>s;
    int di=s.at(k)=='('?1:-1;
    for(int i=k,x=0;0<=i&&i<n;i+=di){
        x+=s.at(i)==s.at(k)?1:-1;
        if(x==0){
            std::cout<<i+1<<std::endl;
            return 0;
        }
    }
}