0

1
  sum := "INT" • [0-1]
  Γ := sum • [0-1]
2
  plus := "PLUS" • [1-2]
3
  sum := "INT" • [2-3]
  sum := sum plus sum • [0-3]
  Γ := sum • [0-3]
4
  plus := "PLUS" • [3-4]
5
  sum := "INT" • [4-5]
  sum := sum plus sum • [2-5]
  sum := sum plus sum • [0-5]
  Γ := sum • [0-5]