def sum_func():
  a = input('Input number 1: ')
  b = input('Input number 2: ')
  sum = float(a) + float(b)
  print('Tong 2 so la: {}'.format(sum))
def try_func():
  try:
    sum_func()
  except :
    print('format error')
    sum_func()
try_func()