input: Write a function to calculate the sum of squares of all the numbers from 1 to N. If the given N is less than 1 then return 0.
  assert sum_of_squares(10)==385
  assert sum_of_squares(5)==55
  assert sum_of_squares(1)==1
  assert sum_of_squares(0)==0
  assert sum_of_squares(-5)==0
output: def sum_of_squares(N):
      if N < 1:
          return 0
      return sum(i**2 for i in range(1, N+1))