fn main() {
    input! {
        m: usize,
        d: usize,
        n: usize,
        b: usize,
    }
    let modulo = b * phi(b);
    let normalize = |a: usize| {
        if a >= modulo {
            a % modulo + modulo
        } else {
            a
        }
    };
    let pow = |mut r: usize, mut n: usize| -> usize {
        let mut t = 1;
        r = normalize(r);
        while n > 0 {
            if n & 1 == 1 {
                t = normalize(t * r);
            }
            r = normalize(r * r);
            n >>= 1;
        }
        t
    };
    let shift = |m: usize| -> usize {
        pow(normalize(m + d), m)
    };
    let mut m = normalize(m);
    let mut n = n;
    let mut t = 0usize;
    let mut pre = vec![None; 2 * modulo];
    while n > 0 {
        if let Some(s) = pre[m] {
            n %= t - s;
        } else {
            pre[m] = Some(t);
        }
        if n > 0 {
            m = shift(m);
            n -= 1;
            t += 1;
        }
    }
    if m % b == 10 {
        println!("A");
    } else {
        println!("{}", m % b);
    }
}

fn phi(a: usize) -> usize {
    let mut res = a;
    for i in 2..=a {
        if a % i == 0 {
            res -= res / i;
        }
    }
    res
}

mod util {
    pub trait Join {
        fn join(self, sep: &str) -> String;
    }

    impl<T, I> Join for I
    where
        I: Iterator<Item = T>,
        T: std::fmt::Display,
    {
        fn join(self, sep: &str) -> String {
            let mut s = String::new();
            use std::fmt::*;
            for (i, v) in self.enumerate() {
                if i > 0 {
                    write!(&mut s, "{}", sep).ok();
                }
                write!(&mut s, "{}", v).ok();
            }
            s
        }
    }
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------
// floor(a ^ (1 / k))
pub fn kth_root(a: u64, k: u64) -> u64 {
    assert!(k > 0);
    if a == 0 {
        return 0;
    }
    if k >= 64 {
        return 1;
    }
    if k == 1 {
        return a;
    }
    let valid = |x: u64| -> bool {
        let mut t = x;
        for _ in 1..k {
            let (val, ok) = t.overflowing_mul(x);
            if !(!ok && val <= a) {
                return false;
            }
            t = val;
        }
        true
    };
    let mut ok = 1;
    let mut ng = 2;
    while valid(ng) {
        ok = ng;
        ng *= 2;
    }
    while ng - ok > 1 {
        let mid = ok + (ng - ok) / 2;
        if valid(mid) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    ok
}