URI Online Judge | 2164
# Fast Fibonacci

**Timelimit: 1**

By M.C. Pinto, UNILA Brazil

Binet's formula is a way to calculate Fibonacci numbers.

Your task is, given a natural number **n**, to compute the value of Fibonacci(**n**) using the formula above.

The input is a natural number **n** (0 < **n** ≤ 50).

The output is the value of Fibonacci(**n**) with 1 decimal place using the given Binet's formula.

Input Samples | Output Samples |

1 |
1.0 |

2 |
1.0 |

3 |
2.0 |