#include <iostream>
#include <algorithm>

using namespace std;


int main()
{
    string s;
    unsigned long int n;
    cin >> s;
    cin >> n;
    cout << (
        //string length * a's count + rest of the string a's cut
        ((n/s.size()) * count(s.begin(),s.end(),'a')) + 
        count(s.begin(),s.begin() + n%s.size(),'a')
    );
    
    return 0;
}