#include <iostream>
#include <string>
using namespace std;
int n,k;
string s;
int main(){
    cin>>n>>k>>s;
    int x=1,num=1,t;
    if(s[k-1]==')')x=-1;
    t=k-1+x;
    while(num){
        if(s[k-1]==s[t])num++;
        else num--;
        t+=x;
    }
    cout<<t-x+1<<endl;
    return 0;
}