fn main() {
    let mut t = String::new();
    std::io::stdin().read_line(&mut t).ok();
    let t: isize = t.trim().parse().unwrap();
    let mut xa = String::new();
    std::io::stdin().read_line(&mut xa).ok();
    let xa: Vec<isize> = xa.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let x = xa[0];
    let a = xa[1];
    let mut yb = String::new();
    std::io::stdin().read_line(&mut yb).ok();
    let yb: Vec<isize> = yb.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let y = yb[0];
    let b = yb[1];

    let (start_cost, start_date) = if t < 0 {
        let unit = t.abs() / b + if t.abs() % b != 0 { 1 } else { 0 };
        (unit * y, unit * b)
    } else {
        (0, 0)
    };
    let mut result = 1isize << 60;
    for i in 0..=a {
        let diff = t + start_date + i*b;
        result = result.min(start_cost + i * y + diff / a * x + diff % a);
    }
    println!("{}", result);
}