scan = string.gmatch(io.read(),"%d+")
n=scan()
m=scan()
p=scan()
q=scan()
r={1,1,1,1,1,1,1,1,1,1,1,1}
n = n - 0

for i = p , p + q - 1 do
  r[i] = 2
end

month = 0
while n > 0 do
  month = month + 1
  n = n - m * r[((month - 1) % 12) + 1] 
end
print(month)