import sys
input = lambda:sys.stdin.readline().strip()

s = input()
k = int(input())
n = len(s)
left = 0
from collections import defaultdict
count = defaultdict(int)
res = 0
    
for right in range(n):
    count[s[right]] += 1
    while count[s[right]] > k:
        count[s[left]] -= 1
        left += 1   
    res += (right - left + 1)
print(res)