In mathematics, the Fibonacci numbers or Fibonacci sequence are the numbers in the following integer sequence: 0,1,1,2,3,5,8,13,21,34,55,89,144
前13的斐波那契數列：0,1,1,2,3,5,8,13,21,34,55,89,144
By definition, the first two numbers in the Fibonacci sequence is 0 and 1, and each subsequent number is the sum of the previous two. In mathematical terms, the sequence Fn of Fibonacci numbers is defined by the relation Fn = Fn-1 + Fn-2 with seed values F0 = 0, F1= 1
斐波那契數由0和1開始，其後的數就由之前的兩個數相加。用數學表示 Fn = (Fn-1) + (Fn-2)，F0 = 0, F1 = 1
Write a program that asks the user to type an integer n, then display Fn on the screen.
寫一個輸入一個整數n，輸出第n個斐波那契數的程式
Example input 1:
5
Example output 1:
5
Example input 2:
12
Example output 2:
144