import sys

def parse(n):
    return int(n)

n=int(input())
l=list(map(parse, input().split(" ")))
l.sort()

if len(set(l)) != len(l):
    print("NO")
    sys.exit()

l2=[]
for i in range(0, len(l) - 1):
    l2.append(l[i + 1] - l[i])
    
length=len(l2)
t=l2[0]
if sum(l2) == t * length:
    print("YES")
else:
    print("NO")