fn main() {
    let mut nmpq = String::new();
    std::io::stdin().read_line(&mut nmpq).ok();
    let nmpq: Vec<usize> = nmpq.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut n = nmpq[0];
    let m = nmpq[1];
    let p = nmpq[2];
    let q = nmpq[3];

    let one_year_leaves = (12 + q) * m;
    let years = n / one_year_leaves;
    n = n % one_year_leaves;
    let mut months = 0;
    if n > 0 {
        for i in 1..12 {
            let leave_leaves: usize = if p <= i && i < p + q { 2 * m } else { m };
            if n <= leave_leaves {
                months = i;
                break;
            } else {
                n -= leave_leaves;
            }
        }
    }
    println!("{}", years * 12 + months);
}