# coding: utf-8
leaves, fall, wind_m, wind_w = map(int, input().split())
calender = [fall for i in range(12)]
for i in range(wind_w):
    calender[(wind_m - 1) + i] = 2 * fall
j = 1
while leaves > 0:
    leaves -= calender[j % 12 - 1]
    j += 1
print(j - 1)