Envío 4780

Código

from collections import Counter
import math

def decrement_and_delete(cnt, c):
    if cnt[c] == 1:
        del cnt[c]
    else:
        cnt[c] -= 1

def min_k(s, k):
    l, r = 0, 0
    w = Counter()
    res = math.inf
    while r < len(s):
        w[s[r]] += 1
        if len(w) == k:
            res = min(res, r - l + 1)
        while l < r  and len(w) >= k:
            decrement_and_delete(w, s[l])
            l += 1
            if len(w) == k:
                res = min(res, r - l + 1)
        r += 1
    return res if res != math.inf else -1

if __name__ == "__main__":
    s = input()
    k = int(input())
    print(min_k(s, k))