#include <bits/stdc++.h>

typedef long long ll;
#define rep(i, b) for(int i = 0; i < b; i++)
#define repi(i, a, b) for(int i = a; i < b; i++)
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define MAX_V 1001
#define MAX_E 401
#define MOD 1000000007
#define EPS 1e-5
#define INF INT_MAX
#define PI 3.141
inline ll toll(std::string s) { ll v; std::istringstream sin(s); sin >> v; return v; }
template<class T> inline std::string toString(T x) { std::ostringstream sout; sout << x; return sout.str(); }
using namespace std;
typedef pair<int, int> pii;

int main()
{
	int N, K;
	string s;
	cin >> N >> K;
	cin >> s;
	
	int depth = 0;
	if (s[K - 1] == '(')
	{
		repi(i, K, s.size())
		{
			if (depth == 0 && s[i] == ')')
			{
				cout << i + 1 << endl;
				return 0;
			}
			else if (s[i] == ')')
			{
				depth--;
				continue;
			}
			depth++;
		}
	}
	else{
		for (int i = K - 2; i >= 0; i--)
		{
			if (depth == 0 && s[i] == '(')
			{
				cout << i + 1 << endl;
				return 0;
			}
			else if (s[i] == '(')
			{
				depth--;
				continue;
			}
			depth++;
		}
	}
	return 0;
}