n,m,p,q = io.read("*n", "*n", "*n", "*n")
year = m * (12 + q)
quot = math.floor(n / year)
rem = n % year
cur = 0
while(0 < rem) do
  cur = cur + 1
  if(cur == 13) then cur = 1 end
  if(p <= cur and cur <= p + q - 1) then
    rem = rem - m * 2
  else
    rem = rem - m
  end
end
print(quot * 12 + cur)