#include <stdio.h>



int main(void){
	int i;
	int N,K;
	int kDepth = 0;
	int depth = 0;
	char S[10100];
	scanf("%d %d", &N, &K);
	scanf("%s", S);
	
	if(S[K-1] == '('){
		for(i=0;i<N;i++){
			if(S[i] == '('){
				depth += 1;
			}
			
			if(kDepth == depth ){
				printf("%d\n", i+1);
				break;
			}
			
			if(K == (i+1)){
				kDepth = depth;
			}
			
			if(S[i] == ')'){
				depth -= 1;
			}
		}
	}else{
		for(i=N-1;i>=0;i--){
			if(S[i] == ')'){
				depth += 1;
			}
			
			if(kDepth == depth ){
				printf("%d\n", i+1);
				break;
			}
			
			if(K == (i+1)){
				kDepth = depth;
			}
			
			if(S[i] == '('){
				depth -= 1;
			}
		}
	}
	
	return 0;
}