//No.22 括弧の対応
#pragma GCC optimize("O3")
#pragma GCC target("avx")
#include <bits/stdc++.h>
#define rep(i ,n) for(int i=0;i<(int)(n);++i)
#define repr(i ,n) for(int i=n;i>(int)(n);--i)
#define rep1(i ,n) for(int i=1;i<=(int)(n);++i)
#define ALL(a) a.begin(), a.end()
#define RSORT(a) sort(ALL(a),greater<>())
#define SORT(a) sort(ALL(a))
#define bit_check(bit, i) ((bit>>(i)) & 1)
#define PRINT(x) cout << (x) << endl;
#define ENDL cout << endl;
using namespace std;
typedef long long int i64;
typedef unsigned long long u64;
template<class T> using V = vector<T>;
using VI = V<int>;
const int INF = 2e9;
const i64 MOD = 1e9 + 7;

template <class T> inline bool chmin(T& a, T b){if(a>b){a=b; return true;} return false;}
template <class T> inline bool chmax(T& a, T b){if(a<b){a=b; return true;} return false;}
struct Init_On{
    Init_On(){
        cin.tie(nullptr);
        ios_base::sync_with_stdio(false);
        cout << fixed << setprecision(16);
    }
};

signed main(){
    int n , k; cin >> n >> k;
    string s; cin >> s;
    VI table(n);
    int i = 0;
    while( s[0] =='(' || s[n-1] == ')' ){
        if( s[i] == 'B' ) { ++i; continue; }
        else if(s[i] == ')'){
            if( s[i-1] == '('){
                s[i] = 'B'; s[i-1] = 'B';
                table[i] = i-1; table[i-1] = i;
                ++i;
            } else {
                for( int j = i -1 ; j >= 0 ; --j ){
                    if( s[j] =='('){
                        s[i] = 'B'; s[j] = 'B';
                        table[i] = j; table[j] = i;
                        ++i;
                        break;
                    }
                }
            }
        } else { ++i; }
    }
    
    /*
    cout << s << endl;
    for ( auto && c : table){
        cout << c << " ";
    }
    ENDL
    */
    
   cout << table[k - 1] + 1 << endl;
}