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::*;
use std::str::*;
use std::cmp::*;

struct Scanner<'a> {
    cin: StdinLock<'a>,
}

impl<'a> Scanner<'a> {
    pub fn new(cin: StdinLock<'a>) -> Scanner<'a> {
        Scanner {
            cin: cin,
        }
    }

    pub fn read<T: FromStr>(&mut self) -> T {
        let s = self.cin.by_ref().bytes().map(|c| c.unwrap() as char)
            .skip_while(|c| c.is_whitespace() || c.is_control())
            .take_while(|c| c.is_alphanumeric())
            .collect::<String>();
        s.parse::<T>().ok().unwrap()
    }
}

fn main(){
    let cin = stdin();
    let cin = cin.lock();
    let mut sc = Scanner::new(cin);

    
    let n: i64 = sc.read();
    let k: i64 = sc.read();
    
    let mut x = 1;
    for _ in 0..n {
        x = min(x * 2, x + k);
    }

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