def sum1(n):
  if n == 0:
    return 0
  return n + sum1(n - 1)

def sum2(n, s):
  if n == 0:
    return s;
  return sum2(n - 1, s + n)

print(sum1(10))
print(sum1(100))
print(sum2(10, 0))
print(sum2(100, 0))