import std.stdio, std.string, std.conv
	,std.array, std.algorithm, std.range
	,std.math;

void main(){
	auto buf = readln().strip().split().map!(to!int)();
	immutable K = buf[1] - 1;

	auto S = readln().strip().to!string;

	int co = 0;
	if(S[K] == '(') {
		foreach(ulong i; K .. S.length) {
			if(S[i] == '(') ++ co;
			else -- co;

			if(co == 0) {
				writeln(i+1);
				break;
			}
		}
	} else {
		foreach_reverse(ulong i; 0 .. K+1) {
			if(S[i] == ')') ++ co;
			else -- co;

			if(co == 0) {
				writeln(i+1);
				break;
			}
		}
	}
}