Problem:
Score : 300 points

Problem Statement

Given is a string S. Let T be the concatenation of K copies of S.
We can repeatedly perform the following operation: choose a character in T and replace it with a different character.
Find the minimum number of operations required to satisfy the following condition: any two adjacent characters in T are different.

Constraints

1 \leq |S| \leq 100

S consists of lowercase English letters.

1 \leq K \leq 10^9

K is an integer.

Input

Input is given from Standard Input in the following format:

S
K

Output

Print the minimum number of operations required.

Sample Input 1

issii
2

Sample Output 1

4

T is issiiissii. For example, we can rewrite it into ispiqisyhi, and now any two adjacent characters are different.

Sample Input 2

qq
81

Sample Output 2

81

Sample Input 3

cooooooooonteeeeeeeeeest
999993333

Sample Output 3

8999939997

Solution in Go (1.6) (judge verdict: Wrong Answer)

package main

import "fmt"

func main() {
	var (
		s string
		k int
	)
	fmt.Scan(&s, &k)

	cnt := 0
	for i := 0; i < len(s); i++ {
		if i+1 < len(s) && s[i] == s[i+1] {
			cnt++
			i++
		}
	}

	if cnt == len(s)-1 {
		fmt.Println(len(s) * k / 2)
		return
	}

	if s[0] != s[len(s)-1] {
		fmt.Println(k * cnt)
		return
	}

	a := 1
	for i := 1; i < len(s); i++ {
		if s[i] != s[0] {
			break
		}
		a++
	}
	b := 1
	for i := len(s) - 2; i >= 0; i-- {
		if s[i] != s[len(s)-1] {
			break
		}
		b++
	}
	cnt = 0
	for i := a; i < len(s)-b; i++ {
		if i+1 < len(s)-b && s[i] == s[i+1] {
			cnt++
			i++
		}
	}
	fmt.Println(k*cnt + (k-1)*((a+b)/2) + a/2 + b/2)
}