#include <iostream>
#include <stack>
using namespace std;
int main(void){
    int a,n,i;
    stack<int> b;
    char ch[10000],m;
    cin>>n>>a>>ch;
    m=ch[a-1];
    if(m=='('){
        for(i=a-1;i<n;i++){
            if(ch[i]=='(') b.push(i);
            else b.pop();
            if(b.empty()) break;
        }
    }else{
        for(i=a-1;i>=0;i--){
            if(ch[i]=='(') b.pop();
            else b.push(i);
            if(b.empty()) break;
        }
    }
    
    cout<<i+1<<"\n";
    return 0;
}