import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import numpy as np

N = int(readline())
X = np.array(read().split(),np.int64)

X.sort()
dx = np.diff(X)

w = dx[0]
answer = 'YES' if  (dx == w).all() else 'NO'
if w == 0:
    answer = 'NO'
print(answer)