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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    agc039a()
}

fun agc039a() {
    val s = readLine()!!
    val k = readLine()!!.toLong()

    if (s.length == 1) return println(k / 2L)

    var lastChar: Char? = null
    val charCount = mutableListOf<Long>()
    for (i in s.indices) {
        if (lastChar != null && s[i] == lastChar) {
            val last = charCount[charCount.lastIndex]
            charCount.removeAt(charCount.lastIndex)
            charCount.add(last + 1L)
        } else {
            charCount.add(1L)
            lastChar = s[i]
        }
    }

    val inside = charCount.map { it / 2L }.sum()

    for (i in s.indices) {
        if (lastChar != null && s[i] == lastChar) {
            val last = charCount[charCount.lastIndex]
            charCount.removeAt(charCount.lastIndex)
            charCount.add(last + 1L)
        } else {
            charCount.add(1L)
            lastChar = s[i]
        }
    }

    val between = charCount.map { it / 2L }.sum() - inside

    for (i in s.indices) {
        if (lastChar != null && s[i] == lastChar) {
            val last = charCount[charCount.lastIndex]
            charCount.removeAt(charCount.lastIndex)
            charCount.add(last + 1L)
        } else {
            charCount.add(1L)
            lastChar = s[i]
        }
    }

    val between2 = charCount.map { it / 2L }.sum() - between - inside

    val answer = inside + if (between == between2) {
        between * (k - 1L)
    } else {
        (between * Math.ceil((k - 1L).toDouble() / 2) + between2 * Math.floor((k - 1).toDouble() / 2)).toLong()
    }

    println(answer)
}