# test7.py

import list

def main () :
  my_list = [14, 198, 47, 918, 405, 578, 46]
  target = 405
  position = 0
  while not my_list == [] and list . head (my_list) <> target :
    my_list = list . tail (my_list)
    position = position + 1;
  if my_list == [] :
    print -1;
  else :
    print position;
  return 0