use std::cmp::*;
use std::io::*;

fn check(v: u128, a: &Vec<u128>, x: u128, y: u128, k: u128) -> u128 {
    let mut res = v * y;
    for i in 0..a.len() {
        let d = a[i].saturating_sub(v * k);
        if d > 1 {
            res += (d - 1 + k - 1) / k * x;
        }
    }
    res
}

fn main() {
    let mut s: String = String::new();
    stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let k: u128 = itr.next().unwrap().parse().unwrap();
    let x: u128 = itr.next().unwrap().parse().unwrap();
    let y: u128 = itr.next().unwrap().parse().unwrap();
    let a: Vec<u128> = (0..n)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();

    let mut r = 1u128 << 60;
    let mut l = 0;
    while r - l > 10 {
        let llr = (l + l + r) / 3;
        let lrr = (l + r + r) / 3;
        let vl = check(llr, &a, x, y, k);
        let vr = check(lrr, &a, x, y, k);
        if vl > vr {
            l = llr;
        } else {
            r = lrr;
        }
    }

    let mut ans = 1u128 << 60;
    for i in l..l + 10 {
        ans = min(ans, check(i, &a, x, y, k));
    }
    println!("{}", ans);
}