# Exponential factorial of N

• Last Updated : 16 Jul, 2021

Given a positive integer N, the task is to print the Exponential factorial of N. Since the output can be very large, print the answer modulus 1000000007

Examples:

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Input: N = 4
Output: 262144

Input: N = 3
Output: 9

Approach: The given problem can be solved based on the following observations:

The exponential factorial is defined by the recurrence relation:

• .

Follow the steps below to solve the problem:

• Initialize a variable say res as 1 to store the exponential factorial of N.
• Iterate over the range [2, N] using the variable i and in each iteration update the res as res = ires%1000000007.
• Finally, after completing the above step, print the answer obtained in res.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach``#include ``using` `namespace` `std;` `// Function to find exponential factorial``// of a given number``int` `ExpoFactorial(``int` `N)``{``  ` `    ``// Stores the exponetial factor of N``    ``int` `res = 1;``    ``int` `mod = 1000000007;` `    ``// Iterare over the range [2, N]``    ``for` `(``int` `i = 2; i < N + 1; i++)``      ` `        ``// Update res``        ``res = (``int``)``pow``(i, res) % mod;` `    ``// Return res``    ``return` `res;``}` `// Driver Code``int` `main()``{``    ``// Input``    ``int` `N = 4;``  ` `    ``// Function call``    ``cout << (ExpoFactorial(N));``  ` `   ``// This code is contributed by Potta Lokesh``    ``return` `0;``}` `// This code is contributed by lokesh potta`

## Java

 `// Java program for the above approach``class` `GFG{``    ` `// Function to find exponential factorial``// of a given number``static` `int` `ExpoFactorial(``int` `N)``{``    ` `    ``// Stores the exponetial factor of N``    ``int` `res = ``1``;``    ``int` `mod = ``1000000007``;` `    ``// Iterare over the range [2, N]``    ``for``(``int` `i = ``2``; i < N + ``1``; i++)``    ` `        ``// Update res``        ``res = (``int``)Math.pow(i, res) % mod;` `    ``// Return res``    ``return` `res;``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ` `    ``// Input``    ``int` `N = ``4``;` `    ``// Function call``    ``System.out.println((ExpoFactorial(N)));``}``}` `// This code is contributed by abhinavjain194`

## Python3

 `# Python3 program for the above approach` `# Function to find exponential factorial``# of a given number`  `def` `ExpoFactorial(N):``    ``# Stores the exponetial factor of N``    ``res ``=` `1``    ``mod ``=` `(``int``)(``1000000007``)` `    ``# Iterare over the range [2, N]``    ``for` `i ``in` `range``(``2``, N ``+` `1``):``        ``# Update res``        ``res ``=` `pow``(i, res, mod)` `    ``# Return res``    ``return` `res`  `# Driver Code` `# Input``N ``=` `4``# Function call``print``(ExpoFactorial(N))`

## C#

 `// C# program for the above approach``using` `System;` `class` `GFG{` `// Function to find exponential factorial``// of a given number``static` `int` `ExpoFactorial(``int` `N)``{``    ` `    ``// Stores the exponetial factor of N``    ``int` `res = 1;``    ``int` `mod = 1000000007;` `    ``// Iterare over the range [2, N]``    ``for``(``int` `i = 2; i < N + 1; i++)``    ` `        ``// Update res``        ``res = (``int``)Math.Pow(i, res) % mod;` `    ``// Return res``    ``return` `res;``}` `// Driver Code``public` `static` `void` `Main()``{``    ``// Input``    ``int` `N = 4;` `    ``// Function call``    ``Console.Write(ExpoFactorial(N));` `}``}` `// This code is contributed by sanjoy_62.`

## Javascript

 ``
Output
`262144`

Time Complexity: O(N*log(N))
Auxiliary Space: O(1)

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