# Find the next fibonacci number

• Difficulty Level : Expert
• Last Updated : 10 Mar, 2021

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

Input: N = 5
Output:
8 is the next fibonacci number after 5
Input: N = 3
Output:

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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`

## Javascript

 ``
Output:
`8`

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