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 = 5Output:8 3 + 5 = 8Input:L = 7, R = 13Output: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 <bits/stdc++.h> ` `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; ` `} ` |

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## 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.. ` ` ` ` ` |

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## 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 ` |

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## 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.. ` |

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## PHP

`<?php ` `//PHP program to print the sum ` `// of all numbers in range L and R ` `// Function to return the sum of ` `// all odd natural numbers ` `function` `sumOdd(` `$n` `) ` `{ ` ` ` `$terms` `= (int)(` `$n` `+ 1) / 2; ` ` ` `$sum` `= ` `$terms` `* ` `$terms` `; ` ` ` `return` `$sum` `; ` `} ` ` ` `// Function to return the sum ` `// of all odd numbers in range L and R ` `function` `suminRange(` `$l` `, ` `$r` `) ` `{ ` ` ` `return` `sumOdd(` `$r` `) - sumOdd(` `$l` `- 1); ` `} ` ` ` `// Driver Code ` ` ` ` ` `$l` `= 2; ` ` ` `$r` `= 5; ` ` ` `echo` `"Sum of odd natural numbers from L to R is "` `, ` ` ` `suminRange(` `$l` `, ` `$r` `); ` ` ` `?> ` |

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**Output:**

Sum of odd natural numbers from L to R is 8

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