#!/usr/bin/python3

n, a, b = map(int, input().split())
w = [int(input()) for i in range(n-1)]

possible = [i for i in range(a, b+1) if min(w + [i]) == a and max(w + [i]) == b]
if len(possible) == 0:
    print (-1)
else:
    print (" ".join(map(str, possible)))