# -*- coding: utf-8 -*-
from sys import stdin

n, m, p, q = [int(x) for x in stdin.readline().rstrip().split()]

cal = [int(0) for i in range(12)]
for i in range(p-1, p-1+q):
    cal[i] += 1

year = n // (m * (12+q))
ans = 12 * year

nokori = n % (m * (12+q))

for i in range(12):
    if cal[i]:
        nokori -= 2*m
    else:
        nokori -= m
    ans += 1
    if nokori <= 0:
        break
print(ans)