#include<stdio.h>
char S[10001];
main(){
    int N,K;
    scanf("%d %d %s",&N,&K,S);
    int count = 0;//(：＋１ )：－１
    if(K < N/2){    //前半の場合
        for(int i = K-1;i < N;i++){
            count += S[i]=='('?1:-1;
            if(count == 0){
                printf("%d\n",i+1);
                return 0;
            }
        }
    }else{
        for(int i = K-1;i >= 0;i--){
            count += S[i]=='('?1:-1;
            if(count == 0){
                printf("%d\n",i+1);
                return 0;
            }
        }
    }
}