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::env;
use std::io::*;
use std::str::*;
use std::mem;
use std::collections::HashMap;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let s = stdin.bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok().unwrap()
}
fn read_char() -> char {
    let c = read::<String>();
    let c = c.chars().collect::<Vec<char>>();
    c[0]
}
fn read_String_Vec() -> Vec<char> {
    let S = read::<String>();
    S.chars().collect::<Vec<char>>()
}

fn vecchar_to_String(Vs: Vec<char>) -> String {
    let mut S = String::new();
    for i in 0..Vs.len() {
        S.push(Vs[i]);
    }
    S
}

/*
A : 65
Z : 90
a : 97
z : 122
*/

/*
let N = read::<i32>();
let S = read::<String>();
let S = read_String_Vec();
let C = read_char();
*/

/*
 .to_string() : * -> String
 &*S          : String -> &str
*/

fn main() {
    // main の引数
    /*
        引数なしのときargs.len() = 1;
    */
    let args: Vec<String> = env::args().collect();

    let N = read::<i32>();
    let K = read::<i32>();
    let mut mlp = 1;
    for n in 0..N {
        if mlp < K {
            mlp *= 2;
        } else {
            mlp += K;
        }
    }
    println!("{}", mlp);

}