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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#include <iostream>
#include <bitset>
using namespace std;

int main() {
    int N, K;

    cin >> N >> K;

    int min = 10000000;

    // ４ビットの全組み合わせループ
    for (int tmp = 0; tmp < (1 << N); tmp++) {

        int D = 1;

        //ビット表現(0000)
        bitset<10> s(tmp);

        for (int i = 0; i < N; i++) {

            if (s.test(i)) {
                D = D * 2;
            }else{
                D = D + K;
            }
        }

        if (min > D){
            min = D;
        }
    }
    cout << min << endl;    

    return 0;

}