#include <bits/stdc++.h> 

using i64 = long long; 
using u64 = unsigned long long; 
using u32 = unsigned; 

using u128 = unsigned __int128; 
using i128 = __int128; 

void solve() {
	int N, K; std::cin >> N >> K;
	std::string S; std::cin >> S;
	K --;
	if(S[K] == '(') {
		int a = 0;
		for(int i = K + 1; i < N; i ++) {
			if(S[i] == '(') a ++;
			else a --;
			if(a < 0) {
				std::cout << i + 1 << "\n";
				return;
			}
		}
	} else {
		int a = 0;
		for(int i = K - 1; i >= 0; i --) {
			if(S[i] == ')') a ++;
			else a --;
			if(a < 0) {
				std::cout << i + 1 << "\n";
				return;
			}
		}
	}
} 

int main() { 
	std::ios::sync_with_stdio(false); 
	std::cin.tie(nullptr); 

	int T = 1; 
	//std::cin >> T; 

	while (T--) { 
		solve(); 
	} 
	return 0; 
}