# import pypyjit
# pypyjit.set_param('max_unroll_recursion=-1')
from collections import defaultdict as dd
S = input
R = range
P = print
def I(): return int(S())
def M(): return map(int, S().split())
def L(): return list(M())
def O(): return list(map(int, open(0).read().split()))
def yn(b): print("Yes" if b else "No")
biga = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
smaa = "abcdefghijklmnopqrstuvwxyz"
def acc(a):
	b = [0]
	for i in a:
		b.append(b[-1] + i)
	return b

n = I()
a = L()
# 1, 2, ..., max(a) が全て a に含まれていれば ok
a.sort()
b = list(set(a))
b.sort()
print("Yes" if b[-1] - b[0] == len(b) - 1 and (n == 1 or any(abs(a[i + 1] - a[i]) == 1 for i in range(n - 1))) and b[0] in [0, 1] else "No")