n=int(input())

a = list(map(int,input().split()))

head = 0

check = {a[0]:0}

ans = 0

for tail in range(1,n):
    if a[tail] in check:
        ans = max(ans, tail-head)
        head = check[a[tail]]+1
        check[a[tail]] = tail
    else:
        check[a[tail]] = 1
    #print(ans)
ans = max(ans, n-head)

print(ans)