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 Rust (1.15.1) (judge verdict: Accepted)

use std::io;
fn main() {
  let stdin = io::stdin();
  let mut buf = String::new();
  stdin
    .read_line(&mut buf)
    .expect("ERROR");
  let n: i64 = buf.trim().parse().unwrap();
  buf = String::new();
  stdin
    .read_line(&mut buf)
    .expect("ERROR");
  //println!("{}",buf);
  let k: i64 = buf.trim().parse().unwrap();

  let mut ans = 1;

  for i in 0..n {
    if ans > k {
      ans = ans + k;
    } else {
      ans = ans + ans;
    }
    //println!("{}",ans);
  }

  println!("{}",ans);
}