proc find[E](a, b: E): int =
  if b.len == 0: return 0
  var i = 0
  while i < a.len:
    var j = i
    var k = 0
    while j < a.len and k < b.len:
      if a[j] != b[k]:
        break
      inc(j)
      inc(k)
    if k == b.len:
      return i
    inc(i)
  return -1