#include <iostream>
#include <sstream>
#include <math.h>
#include <vector>
#include <array>
#include <algorithm>
#include <queue>
#include <numeric>
#include <map>
#include <set>
#include <bitset>

using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define SUM(a) accumulate(ALL(a), 0)
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) printf(__VA_ARGS__)

typedef pair<int, int> pos;
int pos::*x = &pos::first;
int pos::*y = &pos::second;

int dxy[] = {0, 1, 0, -1, 0};

/*================================*/

int N, K;
string S;

signed main()
{
    cin >> N >> K >> S;
    K--;
    int cnt = 0;
    if (S[K] == '(') {
        FOR(i,K+1,N) {
            cnt += (S[i]==')') ? -1 : 1;
            if (cnt < 0) {
                cout << i + 1 << endl;
                return 0;
            }
        }
    } else {
        RREP(i,K) {
            cnt += (S[i]=='(') ? -1 : 1;
            if (cnt < 0) {
                cout << i + 1 << endl;
                return 0;
            }
        }
    }

    return 0;
}