#include <bits/stdc++.h>
using namespace std;

int main() {
    string st;
    cin>>st;
    int n =st.length();
    int k;
    cin>>k;
    int diff=0;
    set<char> s;
    int maxLength=INT_MIN;
    for(int i=0, j=0;j<n;j++){
    	s.insert(st[j]);
    	diff = s.empty() ? 0 : (*s.rbegin() - *s.begin());
		while(diff>k){
			s.erase(st[i]);
			diff = s.empty() ? 0 : (*s.rbegin() - *s.begin());
			i++;
		}
		maxLength=max(maxLength, j-i+1);
	}
	cout<<maxLength;
    return 0;
}