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

void main()
{
  size_t[] rd = readln.split.to!(size_t[]);
  size_t n = rd[0], k = --rd[1];
  string s = readln.chomp;

  size_t r = s[k].predSwitch('(', search(s[k..$]) + k,
                             ')', k - search(s[0..k+1].retro));
  writeln(++r);
}

size_t search(InputRange)(InputRange s)
{
  int d = 0;
  foreach (i, c; s.enumerate) {
    d += c.predSwitch('(', +1, ')', -1);
    if (d == 0) return i;
  }
  return 0;
}