input: Write a function to calculate the sum of the series 1 + ½ + ⅓ + ... + 1/n. If the input is 0 or negative, return 0.
  assert seriesSum(5)==2.283333333333333
  assert seriesSum(1)==1.0
  assert seriesSum(0)==0
  assert seriesSum(-3)==0
  assert seriesSum(10)==2.9289682539682538
output: def seriesSum(n):
      if n <= 0:
          return 0
      return sum(1/i for i in range(1, n+1))