Once upon a time a Catalan who worked as a porter in a building. There, an Arab lived in the penthouse.
The Arab had a problem with your kemorrhages.
One day, the Arab is going down by the lift and has a hemorrhagic attack. When he arrives on the ground floor, the porter realises of your problem and then, he takes out him from the lift, phones an ambulance and goes to the hospital with him.
When they arrive at the hospital, the doctor says:
-"I need urgently 0+ blood".
The Catalonian porter had that type of blood and gave it to him.
The following day, the Arab says him:
-"In thanks for saving my life, I will give you a Rolls Royce car".
The Catalan was very happy.
The next year, the story repeats:
The Arab suffers again a hemorrhagic attack, the porter phones an ambulance and accompanies him at the hospital.
The doctor says again that needs urgently 0+ blood and the porter again give it to him.
The next day, the Arab says:
-"In appreciation for saving my life, I will give you this Harley Davison motorbike".
The Catalan asked himself why this time the Arab gave him a cheaper gift. But, in a short time, felt glad.
The following year, the same event happens. However, this time the Arab gave him only a bicycle.
The Catalan, then, decides to ask:
-"How did you give me a Rolls Royce the first year that I saved your life, the second year only a Harley Davison and the third year only a bicycle? I don´t understand".
And the Arab answers:
-"Blood is doing effect...!!!