n = int(input())
A = list(map(int,input().split()))

ans = 0
last = 0
ind = {}
for i,a in enumerate(A):
    if a not in ind:
        ind[a] = i
    else:
        length = i - ind[a]
        ans = max(ans, length)
        ind[a] = i
        last = i
ans = max(ans, n-last)
print(ans)