use std::io;

fn main() {
    let v = input_nums();
    let (mut n, m, p, q) = (v[0], v[1], v[2], v[3]);

    let mut month;
    let mut count = 0;
    let month_to = if p + q - 1 > 13 { 12 } else { p + q - 1 };
    loop {
        count += 1;
        month = if count % 12 == 0 { 12 } else { count % 12 };
        if p <= month && month <= month_to {
            n -= m * 2;
        } else {
            n -= m;
        }
        if n <= 0 {
            break;
        }
    }
    println!("{}", count);
}

fn input_nums() -> Vec<i64> {
    let mut s = String::new();
    io::stdin().read_line(&mut s).unwrap();
    let mut v = Vec::new();
    for n in s.split_whitespace() {
        v.push(n.parse::<i64>().unwrap());
    }
    v
}