Envío 4175

Código

import math

def find_min_substring(arr, k):
    if k == 1:
        return 1
    i, j = 0, 0
    answer = math.inf
    length = len(arr) 
    while j <= length:
        substring = arr[i:j]
        if len(set(substring)) >= k:
            i += 1
            answer = min(answer, len(substring))
            if answer == k:
                break
            if i == j:
                j += 1
        else:
            j += 1
    return answer

s = input()
k = int(input())
min_substring = find_min_substring(s, k)
print(-1 if min_substring == math.inf else min_substring)