n, m, p, q = map(int, input().split())

mon = [m for i in range(12)]

for i in range(12):
    if i == p:
        for j in range(p-1, min(12,p+q)):
            if j <= 12:
                mon[j] = m * 2
            else:
                break
                            
month = [0] + mon
mo = month[1:]

i, cnt = 1, 0
while n > 0:
    cnt += 1
    n -= mo[i%12]
    i += 1

print(cnt)