import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;
import java.util.List;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Deque;
import java.util.ArrayDeque;
import java.util.Collections;

public class Main {
	public static void main(String[] args) {
		FS reader = new FS();
		// write reader
		int N = reader.nextInt();
		int K = reader.nextInt()-1;
		String S = reader.next();
		if (S.charAt(K) == '(') {
			int cnt = 1;
			for (int i=K+1; i<N; i++) {
				if (S.charAt(i) == '(') cnt++;
				else {
					cnt--;
					if (cnt == 0) {
						System.out.println(i+1);
						break;
					}
				}
			}
		} else {
			int cnt = 1;
			for (int i=K-1; i>=0; i--) {
				if (S.charAt(i) == ')') cnt++;
				else {
					cnt--;
					if (cnt == 0) {
						System.out.println(i+1);
						break;
					}
				}
			}
		}
	}

	public static void output2DArray(boolean[][] a, int r) {
		for (int x=0; x<r; x++) {
			for (int y=0; y<r; y++) {
				if(a[x][y]) System.out.print("o");
				else System.out.print("x");
			}
			System.out.println();
		}
		System.out.println();
	}
	
	public static void outputArray(long[] a) {
		int size = a.length;
		for (int i=0; i<size; i++) {
			if (i == size-1) System.out.print(a[i]);
			else System.out.print(a[i] + " ");
		}
		System.out.println();
	}

	public static void outputList(ArrayList a) {
		int size = a.size();
		for (int i=0; i<size; i++) {
			if (i == size-1) System.out.print(a.get(i));
			else System.out.print(a.get(i) + " ");
		}
		System.out.println();
	}
	
	// Read Class
	static class FS {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;
		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}
	
		private int readByte() { return hasNextByte() ? buffer[ptr++] : -1;}
		private boolean isPrintableChar(int c) {return 33 <= c && c <= 126;}
		private void skipUnprintable() {while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
	
		public boolean hasNext() { skipUnprintable(); return hasNextByte();}
		public String next() {
			if (!hasNext()) throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while(isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
		public int nextInt() {
			return (int)nextLong();
		}
		public long nextLong() {
			if (!hasNext()) throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while(true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if(b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}
	}
}