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# Sum of all odd natural numbers in range L and R

• Last Updated : 28 Aug, 2022

Given two integers L and R, the task is to find the sum of all odd natural numbers in range L and R inclusive.
Examples:

```Input: L = 2, R = 5
Output: 8
3 + 5 = 8

Input: L = 7, R = 13
Output: 40```

A naive approach is to traverse from L to R and summate the elements to get the answer.
An efficient approach is to use the formula for calculating the sum of all odd natural numbers upto R and L-1 and then subtract sum(R)-sum(L-1).
Below is the implementation of the above approach:

## C++

 `// C++ program to print the sum` `// of all numbers in range L and R` `#include ` `using` `namespace` `std;`   `// Function to return the sum of` `// all odd natural numbers` `int` `sumOdd(``int` `n)` `{` `    ``int` `terms = (n + 1) / 2;` `    ``int` `sum = terms * terms;` `    ``return` `sum;` `}`   `// Function to return the sum` `// of all odd numbers in range L and R` `int` `suminRange(``int` `l, ``int` `r)` `{` `    ``return` `sumOdd(r) - sumOdd(l - 1);` `}`   `// Driver Code` `int` `main()` `{` `    ``int` `l = 2, r = 5;` `    ``cout << ``"Sum of odd natural numbers from L to R is "` `         ``<< suminRange(l, r);`   `    ``return` `0;` `}`

## Java

 `// Java program to print the sum` `// of all numbers in range L and R`   `import` `java.io.*;`   `class` `GFG {` `   `      `// Function to return the sum of` `// all odd natural numbers` `static` `int` `sumOdd(``int` `n)` `{` `    ``int` `terms = (n + ``1``) / ``2``;` `    ``int` `sum = terms * terms;` `    ``return` `sum;` `}`   `// Function to return the sum` `// of all odd numbers in range L and R` `static` `int` `suminRange(``int` `l, ``int` `r)` `{` `    ``return` `sumOdd(r) - sumOdd(l - ``1``);` `}`   `// Driver Code` `public` `static` `void` `main (String[] args) {` `            ``int` `l = ``2``, r = ``5``;` `    ``System.out.print( ``"Sum of odd natural numbers from L to R is "` `        ``+ suminRange(l, r));` `    ``}` `}` `// This code is contributed by shs..`

## Python3

 `# Python 3 program to print the sum ` `# of all numbers in range L and R `   `# Function to return the sum of ` `# all odd natural numbers ` `def` `sumOdd(n):` `    ``terms ``=` `(n ``+` `1``)``/``/``2` `    ``sum1 ``=` `terms ``*` `terms` `    ``return` `sum1`   `# Function to return the sum ` `# of all odd numbers in range L and R ` `def` `suminRange(l, r):` `    ``return` `sumOdd(r) ``-` `sumOdd(l ``-` `1``)` `    `  `# Driver code` `l ``=` `2``; r ``=` `5` `print``(``"Sum of odd natural number"``,` `      ``"from L to R is"``, suminRange(l, r))`   `# This code is contributed by Shrikant13`

## C#

 `// C# program to print the sum` `// of all numbers in range L and R` `using` `System;`   `class` `GFG ` `{` `    `  `// Function to return the sum of` `// all odd natural numbers` `static` `int` `sumOdd(``int` `n)` `{` `    ``int` `terms = (n + 1) / 2;` `    ``int` `sum = terms * terms;` `    ``return` `sum;` `}`   `// Function to return the sum` `// of all odd numbers in range L and R` `static` `int` `suminRange(``int` `l, ``int` `r)` `{` `    ``return` `sumOdd(r) - sumOdd(l - 1);` `}`   `// Driver Code` `public` `static` `void` `Main () ` `{` `    ``int` `l = 2, r = 5;` `    ``Console.WriteLine( ``"Sum of odd natural numbers "` `+ ` `                ``"from L to R is "` `+ suminRange(l, r));` `}` `}`   `// This code is contributed by shs..`

## PHP

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## Javascript

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Output:

`Sum of odd natural numbers from L to R is 8`

Time Complexity: O(1)

Auxiliary Space: O(1), since no extra space has been taken.

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