const INF: isize = 1isize << 60;

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 mut result = INF;
    let offset = if t > 0 { 0 } else { t.abs() / b + if t.abs() % b > 0 { 1 } else { 0 } };
    let date_offset = offset * y;
    let offset = offset * -b;
    for i in 0..=t.abs() {
        let offset = offset - i*b;
        let mut costs = date_offset + i*y;
        costs = costs + (t - offset) / a * x + (t - offset) % a;
        result = result.min(costs);
    }
    println!("{}", result);
}