#!/bin/python3

import math
import os
import random
import re
import sys

# Complete the repeatedString function below.
def repeatedString(s, n):
    count = 0
    for i in s:
        if i == 'a':
            count = count + 1

    length = len(s);
    num_repeat = math.floor(n/length);

    total_count_a = num_repeat * count;

    #handle remainder
    remaining_letters = n - (num_repeat * length)

    for i in range(0, remaining_letters):
        if s[i] == 'a':
            total_count_a += 1

    return total_count_a



if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    s = input()

    n = int(input())

    result = repeatedString(s, n)

    fptr.write(str(result) + '\n')

    fptr.close()