input: Write a python function to find the sum of integers from 1 to a given number using recursion.
  assert find_sum(5) == 15
  assert find_sum(10) == 55
  assert find_sum(0) == 0
output: def find_sum(n):
      if n == 0:
          return 0
      else:
          return n + find_sum(n - 1)