n = int(input())
x = list(map(int,input().split()))
x_so = sorted(x)
x_set = set(x)

for i in range(1, n):
    if i == 1:
        che = x_so[i - 1] - x_so[i]
    elif (che != x_so[i - 1] - x_so[i]) or len(x_set) != len(x):
        print('NO')
        break
    elif i == n - 1:
        if che == x_so[i - 1] - x_so[i]:
           print('Yes')