input: Write a function to compute the sum of two variables and store the result in a third variable. Then print the result. Given x and y, the function should return the sum of x and y.
  assert compute_sum(5, 8)==13
  assert compute_sum(3, 4)==7
  assert compute_sum(-1, 1)==0
  assert compute_sum(0, 0)==0
  assert compute_sum(-5, -3)==-8
output: def compute_sum(x, y):
      return x + y