use std::collections::{HashMap, HashSet};

fn main() {
    proconio::input! {
        n: u64,
    }
    let mut dp = (0u64, 1u64);
    for n in 0..n {
        dp = (dp.1, dp.0 + dp.1);
        eprintln!("{:?}", dp);
    }
    println!("{}", dp.1);
}