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: Wrong Answer)

import java.math.BigInteger;
import kotlin.system.exitProcess;

fun main(args: Array<String>){
  val s = readLine()!!
  val k = BigInteger(readLine())

  if( s.length == 1 ){
    println(k.divide(BigInteger("2")))
    exitProcess(0)
  }

  if( s.length % 2 == 1 ){
    var i = 1;
    while(i < s.length){
      if( s[0] != s[i] )
        break;
      i++;
    }
    if( i == s.length ){
      println(k.multiply(BigInteger(s.length.toString())).divide(BigInteger("2")));
      exitProcess(0);
    }
  }

  var result = 0;

  var i = 1;
  while( i < s.length+1 ){
    if( i < s.length && s[i] == s[i-1] ){
      result++;
      i++;
    }else if( i == s.length && s[s.length-1] == s[0] )
      result++;

    i++;
  }

  if( s[0] == s[s.length-1] ){
    var tmpL = 1;
    while( tmpL < s.length && s[0] == s[tmpL] )
      tmpL++;
    var tmpR = 1;
    while( tmpR < s.length && s[0] == s[s.length-1-tmpR] )
      tmpR++;
    if( tmpL % 2 == 0 && tmpR % 2 == 1 )
      result--;
  }

  println(BigInteger(result.toString()).multiply(k));
}