#include <stdio.h>
#include <stdlib.h>
int main()
{
  int N, K;
  char* S;
  scanf("%d", &N);
  scanf("%d", &K);
  S = (char*)malloc(N+1);
  scanf("%s", S);

  int ans;
  if (S[K-1] == '(' /*)*/ ) {
    int i;
    int count = 1;
    for (i=K; i<N; i++) {
      if (S[i] == '(' /*)*/ ) {
        count++;
      } else {
        count--;
      }
      if (count == 0) break;
    }
    ans = i+1;
  } else {
    int* work;
    int top = 0;
    work = (int*)malloc(sizeof(int)*K);
    int i;
    int end = K-1;
    for (i=0; i<end; i++) {
      if (S[i] == '(' /*)*/ ) {
        work[top] = i;
        top++;
      } else {
        top--;
      }
    }
    ans = work[top-1] + 1;
  }
  printf("%d\n", ans);
  return 0;
}