use cht_integer::ConvexHullTrick;
#[allow(unused_imports)]
#[cfg(feature = "dbg")]
use dbg::lg;
use proconio::{fastout, input};
use std::iter::once;

#[fastout]
fn main() {
    input! {
        n: usize,
        a: i64,
        b: i64,
        w: i64,
        d: [i64; n],
    }
    let mut cht = ConvexHullTrick::new();
    cht.insert(0, -(2 * w));
    for (i, d) in once(0).chain(d.iter().copied()).enumerate() {
        let x0 = i as i64;
        let y0 = (-cht.eval(x0) + b * x0 * x0) / 2 + d;
        let tilt = -2 * a + (-2 * x0 - 1) * b;
        let intercept = 2 * y0 + 2 * (x0 + 1) * a + b * x0 * (x0 + 1);
        cht.insert(-tilt, -intercept);
    }
    let end = n as i64 + 1;
    let ans = (-cht.eval(end) + b * end * end) / 2;
    println!("{}", ans);
}

// cht_integer {{{
#[allow(dead_code)]
mod cht_integer {
    use std::{
        borrow::Borrow,
        collections::BTreeSet,
        fmt::Debug,
        i64::{MAX, MIN},
    };
    #[derive(Clone, Debug, Default, Hash, PartialEq)]
    pub struct ConvexHullTrick {
        set: BTreeSet<Segment>,
    }
    impl ConvexHullTrick {
        pub fn new() -> Self {
            Self::default()
        }
        pub fn multieval(&self, xs: impl Iterator<Item = i64>) -> Vec<i64> {
            xs.map(|x| self.eval(x)).collect()
        }
        pub fn collect_lines(&self) -> Vec<(i64, i64)> {
            self.set
                .iter()
                .map(|&seg| (seg.line.p, -seg.line.q))
                .collect()
        }
        pub fn eval(&self, x: i64) -> i64 {
            assert!(
                !self.set.is_empty(),
                "empty maximum is the negative infinity"
            );
            self.set.range(Max(x)..).next().unwrap().line.eval(x)
        }
        pub fn lave(&self, p: i64) -> Option<i64> {
            assert!(
                !self.set.is_empty(),
                "empty maximum is the negative infinity"
            );
            let &Segment {
                line: Line { p: p1, q: q1 },
                min: Min(min),
                max: _,
            } = self.set.range(p..).next()?;
            if min == MIN {
                if p1 == p {
                    Some(q1)
                } else {
                    None
                }
            } else {
                Some(q1 - (p1 - p) * min)
            }
        }
        pub fn insert(&mut self, tilt: i64, intercept: i64) -> bool {
            let q = -intercept;
            let p = tilt;
            if !self.set.is_empty() && self.lave(p).map_or(false, |c| c <= q) {
                return false;
            }
            self.set.take(&p);
            let line = Line { p, q };
            while let Some(&seg1) = self.set.range(..p).next_back() {
                if seg1.min.0 == MIN || line.eval(seg1.min.0) < seg1.line.eval(seg1.min.0) {
                    break;
                }
                self.set.remove(&seg1);
            }
            while let Some(&seg1) = self.set.range(p..).next() {
                if seg1.max.0 == MAX || line.eval(seg1.max.0) < seg1.line.eval(seg1.max.0) {
                    break;
                }
                self.set.remove(&seg1);
            }
            if let Some(&seg1) = self.set.range(..p).next_back() {
                self.set.remove(&seg1);
                match seg1.line.brace(line) {
                    Err(x) => {
                        debug_assert!(seg1.min.0 < x);
                        self.set.insert(Segment {
                            max: Max(x),
                            ..seg1
                        });
                    }
                    Ok(brace) => {
                        if seg1.min.0 < brace.min.0 {
                            self.set.insert(Segment {
                                max: Max(brace.min.0),
                                ..seg1
                            });
                        }
                        self.set.insert(brace);
                    }
                }
            }
            if let Some(&seg1) = self.set.range(p..).next() {
                self.set.remove(&seg1);
                match line.brace(seg1.line) {
                    Err(x) => {
                        debug_assert!(x < seg1.max.0);
                        self.set.insert(Segment {
                            min: Min(x),
                            ..seg1
                        });
                    }
                    Ok(brace) => {
                        if brace.max.0 < seg1.max.0 {
                            self.set.insert(Segment {
                                min: Min(brace.max.0),
                                ..seg1
                            });
                        }
                        self.set.insert(brace);
                    }
                }
            }
            let min = Min(self
                .set
                .range(..p)
                .next_back()
                .map_or(MIN, |seg1| seg1.max.0));
            let max = Max(self.set.range(p..).next().map_or(MAX, |seg1| seg1.min.0));
            if min.0 < max.0 {
                self.set.insert(Segment { line, min, max });
            }
            true
        }
    }
    #[derive(Clone, Debug, Default, Hash, PartialEq, Eq, PartialOrd, Ord, Copy)]
    struct Min(i64);
    #[derive(Clone, Debug, Default, Hash, PartialEq, Eq, PartialOrd, Ord, Copy)]
    struct Max(i64);
    #[derive(Clone, Debug, Default, Hash, PartialEq, Eq, PartialOrd, Ord, Copy)]
    struct Line {
        p: i64,
        q: i64,
    }
    impl Line {
        fn eval(&self, x: i64) -> i64 {
            self.p * x - self.q
        }
        fn brace(self, other: Self) -> Result<Segment, i64> {
            let Self { p: p0, q: q0 } = self;
            let Self { p: p1, q: q1 } = other;
            debug_assert!(p0 < p1);
            let x0 = (q1 - q0).div_euclid(p1 - p0);
            if x0 * (p1 - p0) == (q1 - q0) {
                return Err(x0);
            }
            let x1 = x0 + 1;
            let p = (p1 * x1 - p0 * x0) - (q1 - q0);
            let q = (p1 - p0) * x0 * x1 - q1 * x0 + q0 * x1;
            debug_assert_eq!(p * x0 - q, p0 * x0 - q0);
            debug_assert_eq!(p * x1 - q, p1 * x1 - q1);
            Ok(Segment {
                line: Self { p, q },
                min: Min(x0),
                max: Max(x1),
            })
        }
    }
    #[derive(Clone, Default, Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Copy)]
    struct Segment {
        line: Line,
        min: Min,
        max: Max,
    }
    impl Borrow<i64> for Segment {
        fn borrow(&self) -> &i64 {
            &self.line.p
        }
    }
    impl Borrow<Min> for Segment {
        fn borrow(&self) -> &Min {
            &self.min
        }
    }
    impl Borrow<Max> for Segment {
        fn borrow(&self) -> &Max {
            &self.max
        }
    }
}
// }}}
// template {{{
#[cfg(not(feature = "dbg"))]
#[allow(unused_macros)]
#[macro_export]
macro_rules! lg {
    ($($expr:expr),*) => {};
}
// }}}