Envío 3459

Código

import math

def shortest_substring_k_distinct(s, k = 1):
    if k == 1:
        return 1
    
    shortest_substring_size = math.inf
    window_start = 0
    char_freq = {}

    for window_end, current in enumerate(s):
        if current in char_freq:
            char_freq[current] = char_freq[current] + 1
        else: 
            char_freq[current] = 1

        while len(char_freq) == k:
            shortest_substring_size = min(shortest_substring_size, (window_end + 1) - window_start)
            
            # Shorten window to the left
            prev = s[window_start]

            if char_freq[prev] == 1:
                char_freq.pop(prev)
            else:
                char_freq[prev] = char_freq[prev] - 1

            window_start += 1
            

    return -1 if math.isinf(shortest_substring_size) else shortest_substring_size

s = input()
k = int(input())
        
print(shortest_substring_k_distinct(s, k))