input: Write a python function to convert temperatures between Celsius and Fahrenheit.
  assert cToF(0) == 32
  assert cToF(100) == 212
  assert fToC(32) == 0
  assert fToC(212) == 100
output: def cToF(celsius):
      return celsius * 9/5 + 32
  
  def fToC(fahrenheit):
      return (fahrenheit - 32) * 5/9