701 B | 701 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from decimal import Decimal
BLANK = " "
# inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n, a, b = mii()
l = [ii() for _ in range(n - 1)]
mn = min(l)
mx = max(l)
if (mn < a or mx > b) or (mn != a and mx != b):
p(-1)
elif mn == a and mx == b:
for i in range(a, b + 1):
p(i)
elif mn != a:
p(a)
else:
p(b)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()