input: Write a python function to calculate the total of all even natural numbers between l and r.
  assert sum_Even(2,5) == 6
  assert sum_Even(3,8) == 18
  assert sum_Even(4,6) == 10
output: def sum_Even(l, r):
      return sum(i for i in range(l, r + 1) if i % 2 == 0)