#include <cstdio>

#define FOR(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define REV(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define INC0(i, n) FOR(i, 0, n)
#define INC1(i, n) FOR(i, 1, (n) + 1)
#define DEC0(i, n) REV(i, 0, n)
#define DEC1(i, n) REV(i, 1, (n) + 1)

typedef long long   signed int LL;
typedef long long unsigned int LU;


int n, k;
char s[10001];

int main() {
	scanf("%d%d", &n, &k); k--;
	scanf("%s", s);
	
	int ans;
	
	if(s[k] == '(' ) {
		int d = 0;
		FOR(i, k, n) {
			if(s[i] == '(' ) { d++; }
			else             { d--; }
			
			if(d == 0) { ans = i; }
		}
	} else {
		int d = 0;
		REV(i, 0, k + 1) {
			if(s[i] == ')' ) { d++; }
			else             { d--; }
			
			if(d == 0) { ans = i; }
		}
	}
	
	printf("%d\n", ans + 1);
	
	return 0;
}