def minimumDistances(a):
    min_d = 10000
    
    for i in range(len(a)-1):
        for j in range(i+1, len(a)):
            if (a[i] == a[j]):
                min_d = min(min_d, abs(i-j))
    
    return -1 if min_d == 10000 else min_d

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

result = minimumDistances(a)

print(result)