Problem:
Score : 200 points

Problem Statement

Square1001 has seen an electric bulletin board displaying the integer 1.
He can perform the following operations A and B to change this value:

Operation A: The displayed value is doubled.

Operation B: The displayed value increases by K.

Square1001 needs to perform these operations N times in total.
Find the minimum possible value displayed in the board after N operations.

Constraints

1 \leq N, K \leq 10

All input values are integers.

Input

Input is given from Standard Input in the following format:

N
K

Output

Print the minimum possible value displayed in the board after N operations.

Sample Input 1

4
3

Sample Output 1

10

The value will be minimized when the operations are performed in the following order: A, A, B, B.

In this case, the value will change as follows: 1 → 2 → 4 → 7 → 10.

Sample Input 2

10
10

Sample Output 2

76

The value will be minimized when the operations are performed in the following order: A, A, A, A, B, B, B, B, B, B.

In this case, the value will change as follows: 1 → 2 → 4 → 8 → 16 → 26 → 36 → 46 → 56 → 66 → 76.

By the way, this contest is AtCoder Beginner Contest 076.

Solution in Scala (2.11.7) (judge verdict: Accepted)

object Main extends App {
    val scanner = new java.util.Scanner(System.in)
    val n = scanner.next().toInt
    val k = scanner.next().toInt
    println(sim(1, k, n).min)
    
    def sim(n: Int, k: Int, cnt: Int): List[Int] = {
        if (cnt == 0) { 
            List(n)
        } else {
            sim(n+k, k, cnt-1) ::: sim(n*2, k, cnt-1)
        }
    }
}