# Find the next fibonacci number

Given a fibonacci number N, the task is to find the next fibonacci number.

Examples:

Input: N = 5
Output: 8
8 is the next fibonacci number after 5

Input: N = 3
Output: 5

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The ratio of two adjacent numbers in the Fibonacci series rapidly approaches ((1 + sqrt(5)) / 2). So if N is multiplied by ((1 + sqrt(5)) / 2) and round it, the resultant number will be the next fibonacci number.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return the next ` `// fibonacci number ` `int` `nextFibonacci(``int` `n) ` `{ ` `    ``double` `a = n * (1 + ``sqrt``(5)) / 2.0; ` `    ``return` `round(a); ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `n = 5; ` `    ``cout << nextFibonacci(n); ` `} ` ` `  `// This code is contributed by mohit kumar 29 `

## Java

 `// Java implementation of the approach  ` `class` `GFG ` `{ ` `     `  `    ``// Function to return the next ` `    ``// fibonacci number ` `    ``static` `long` `nextFibonacci(``int` `n) ` `    ``{ ` `        ``double` `a = n * (``1` `+ Math.sqrt(``5``)) / ``2.0``; ` `        ``return` `Math.round(a); ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `main (String[] args) ` `    ``{ ` `        ``int` `n = ``5``; ` `        ``System.out.println(nextFibonacci(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by AnkitRai01 `

## Python3

 `# Python3 implementation of the approach ` `from` `math ``import` `*` ` `  `# Function to return the next  ` `# fibonacci number ` `def` `nextFibonacci(n): ` `    ``a ``=` `n``*``(``1` `+` `sqrt(``5``))``/``2.0` `    ``return` `round``(a) ` ` `  `# Driver code ` `n ``=` `5` `print``(nextFibonacci(n)) `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG  ` `{ ` `     `  `    ``// Function to return the next ` `    ``// fibonacci number ` `    ``static` `long` `nextFibonacci(``int` `n) ` `    ``{ ` `        ``double` `a = n * (1 + Math.Sqrt(5)) / 2.0; ` `        ``return` `(``long``)Math.Round(a); ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``int` `n = 5; ` `        ``Console.WriteLine(nextFibonacci(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by 29AjayKumar `

Output:

```8
```

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