#include<bits/stdc++.h>
using namespace std;
typedef long long ll ;
ll T=1;const ll N=1e5+5;
ll a[N];ll n;ll ans;ll x,y;string s;
map<char,ll>vis;
bool check(ll l,ll r){
	for(ll i=l;i<=r;++i){
		if(vis[s[i]]>x)return 0;
	}return 1;
}
ll cnt;
void solve(){
	
	cin>>s;n=s.size();
	s=" "+s;
	cin >>x;
	ll l=1;ll  r=1;
	while(r<=n){
		vis[s[r]]++;
		while(vis[s[r]]>x){
			vis[s[l]]--;
			l++;
		}
		cnt+=r-l+1;
		r++;
		
		
	}
	cout<<cnt;
	

}
int main(){
	while(T--)solve();
	return 0;
}

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)