文字式比例尺：图上1厘米相当于实地距离100千米，表示成数字式是    

为了求1+2+2²+2³+…+2²⁰¹¹+2²⁰¹²的值，可令S=1+2+2²+2³+…+2²⁰¹¹+2²⁰¹²，则2S=2+2²+2³+2⁴+…+2²⁰¹²+2²⁰¹³，因此2S﹣S=2²⁰¹³﹣1，所以1+2²+2³+…+2²⁰¹²=2²⁰¹³﹣1．仿照以上方法计算1+5+5²+5³+…+5²⁰¹²的值是（　　）​

   John is my best friend. We live in the same building. We study in the same school but not in the same class. We often play football together after school. We have been good friends for two years.
   John is tall and strong with black hair. He has a round face, a small nose and big, brown eyes. I like his eyes because they are always bright and smiling.
   John is always friendly and helpful. When I feel bored or unhappy, he tells me funny jokes and makes me laugh. He'll give me help when I need.
   John is very smart. He reads a lot of books. He is good at singing and acts very well. He would like to make people happy with his songs and performance when he grows up. I believe that he can become as popular as Jackie Chan and travel around the world in the future.