input: Write a function to calculate the sum of squares of all the numbers from 1 to N.
  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(15)==1240
output: def sum_of_squares(N):
      return sum(i**2 for i in range(1, N+1))