儿童节快到了，班长想要给班上的每个同学给一个巧克力，巧克力的形状是一个宽为2，长为n的长方形，由于巧克力太贵，班长就想把这个大块的巧克力分成许多

1*2（宽*长）的小块巧克力，这样每个人都能得到一份1*2的巧克力，现在给定巧克力的长为正整数n（1<=n<=91），请你判断对于这个2*n的巧克力有多少种不同的分法？

这道题考察的是斐波那契数列。-Children' s Day is coming, the squad leader wanted to give each student in the class to a chocolate, chocolate shape is a width of 2 and a length of n rectangular, as chocolate is too expensive, we want this monitor into a number of chunks of chocolate 1* 2 (W* L) of the small piece of chocolate, chocolate so that everyone can get a 1* 2, now given chocolate length is a positive integer n (1 < = n < = 91), you judge For this 2* n chocolate How many different points system? This question is examined Fibonacci number.