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## 题目描述

The Fibonacci Numbers{0,1,1,2,3,5,8,13,21,34,55...} are defined by the recurrence:
F0=0 F1=1 Fn=Fn-1+Fn-2,n>=2
Write a program to calculate the Fibonacci Numbers.

## 输入

Each case contains a number n and you are expected to calculate Fn.(0<=n<=30) 。

## 输出

For each case, print a number Fn on a separate line,which means the nth Fibonacci Number.

## 样例输入

1

## 样例输出

1

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