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)


#[allow(dead_code)]
const MOD: usize = 1_000000000 + 7;

fn main() {
    let mut cin = Scanner::new();
    let n = cin.next_isize();
    let k = cin.next_isize();
    let mut ans = 1;
    for _ in 0..n {
        ans = std::cmp::min(ans * 2, ans + k);
    }
    println!("{}", ans);
}


struct Scanner {
    reader: std::io::Stdin,
    tokens: std::collections::VecDeque<String>,
}

impl Scanner {
    fn new() -> Self {
        Scanner {
            reader: std::io::stdin(),
            tokens: std::collections::VecDeque::new(),
        }
    }

    fn next(&mut self) -> String {
        if self.tokens.is_empty() {
            let mut s = String::new();
            loop {
                self.reader.read_line(&mut s).ok();
                let s = s.trim();
                if s.len() != 0 {
                    for it in s.split_whitespace() {
                        self.tokens.push_back(it.into())
                    }
                    break;
                }
            }
        }
        self.tokens.pop_front().unwrap()
    }

    fn next_generics<T>(&mut self) -> T where
        T: std::str::FromStr + std::marker::Copy,
        <T as std::str::FromStr>::Err: std::fmt::Debug
    {
        self.next().parse().unwrap()
    }
    
    #[allow(dead_code)] fn next_i32(&mut self) -> i32 { self.next_generics::<i32>() }
    #[allow(dead_code)] fn next_i64(&mut self) -> i64 { self.next_generics::<i64>() }
    #[allow(dead_code)] fn next_u64(&mut self) -> u64 { self.next_generics::<u64>() }
    #[allow(dead_code)] fn next_usize(&mut self) -> usize { self.next_generics::<usize>() }
    #[allow(dead_code)] fn next_isize(&mut self) -> isize { self.next_generics::<isize>() }
}