use std::io::{self, *};

struct Solution{

}

impl Solution{
  pub fn fib(n: i32) -> i32 {
    if n <= 2 {
        return 1;
    }
    return Solution::fib(n-1) + Solution::fib(n-2);
  }
}

fn main() {
    let mut n : i32 = 0;
    let mut input = String::new();
    io::stdin().read_line(&mut input);
    n = input.trim().parse().expect("");
    print!("{}", Solution::fib(n));
}