<reponame>terror/Solutions<gh_stars>1-10
def main():
  n = int(input())
  s = sorted(list(map(int, input().split())))
  print("possible" if check(s) else "impossible")

def check(s):
  for i in range(len(s) - 2):
    if s[i] + s[i + 1] > s[i + 2]:
      return True
  return False

main()

def main():
  n = int(input())
  s = sorted(list(map(int, input().split())))
  print("possible" if check(s) else "impossible")

def check(s):
  for i in range(len(s) - 2):
    if s[i] + s[i + 1] > s[i + 2]:
      return True
  return False

main()