from collections import Counter
n = int(input())
elements = list(map(int, input().split(' ')))
print("-1" if len(set(elements)) == n else "", end="")
if len(set(elements)) != n:
    repeated_list = [_ for _ in Counter(elements) if Counter(elements).get(_) > 1]
    less_distance = []
    for i in repeated_list:
        indices = [index for index, j in enumerate(elements) if j == i]
        less_distance.append(abs(indices[0] - indices[1]))
    print(min(less_distance))