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

fn main() {
    proconio::input! {
        pqr: [u64;3],
        k: usize,
    }
    if k <= 3 {
        println!("{}", pqr[k - 1]);
        return;
    }
    let first = [pqr[0] % 10, pqr[1] % 10, pqr[2] % 10];
    let mut pqr: [u64; 3] = pqr.try_into().unwrap();
    let mut shuuki = 0;
    loop {
        pqr = [pqr[1], pqr[2], (pqr[0] + pqr[1] + pqr[2]) % 10];
        shuuki += 1;
        if pqr == first {
            break;
        }
    }
    let k = (k - 3) % shuuki;
    for _ in 0..k {
        pqr = [pqr[1], pqr[2], (pqr[0] + pqr[1] + pqr[2]) % 10];
    }
    eprintln!("{shuuki}");
    eprintln!("{:?}", pqr);
    println!("{}", pqr[2]);
}