local b0, c0 = io.read("*n", "*n")
local b1, c1 = io.read("*n", "*n")
c0 = (c0 + b0 * 200) % b0
c1 = (c1 + b1 * 200) % b1

for i = 0, 100000 do
  if i % b0 == c0 and i % b1 == c1 then
    print(i)
    os.exit()
  end
end
print("NaN")