程序接收由用户键入的数N，根据给定的N值，计算Fibonacci数。 Fibonacci数的定义如下： FIB（1）=1 FIB（2）=1 FIB（N）=FIB（N-2）+FIB（N-1） N>=3-Typed by the user program receives the number N, according to the given value of N, calculate the Fibonacci numbers. Fibonacci numbers

计算斐波那契数列，F0=0, F1=1, Fn=Fn-1+Fn-2 (n>=2) -calculate the sequence fibonacci