N, M, P, Q = map(int, raw_input().split())
fallleaf = [M, M, M, M, M, M, M, M, M, M, M, M]
for i in range(P, P+Q):
	fallleaf[i%12] += M
month = 1
while True:
	N -= fallleaf[month%12]
	if N <= 0: break
	month += 1
print month