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Sum of all natural numbers in range L to R
• Last Updated : 05 Apr, 2021

Given a range L and R, the task is to find the sum of all natural numbers in range L to R.
Examples

```Input: L = 2, R = 5
Output: 14
2 + 3 + 4 + 5 = 14

Input: L = 10, R = 20
Output: 165```

A naive approach is to traverse from L to R and add all the elements one by one to get the sum.
An efficient approach is to use the formula for the sum of first N natural numbers. The idea of the inclusion-exclusion principle helps to solve the above problem. Find the sum of natural numbers till 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 natural numbers``int` `sumNatural(``int` `n)``{``    ``int` `sum = (n * (n + 1)) / 2;``    ``return` `sum;``}` `// Function to return the sum``// of all numbers in range L and R``int` `suminRange(``int` `l, ``int` `r)``{``    ``return` `sumNatural(r) - sumNatural(l - 1);``}` `// Driver Code``int` `main()``{``    ``int` `l = 2, r = 5;``    ``cout << ``"Sum of 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` `class` `GFG{``// Function to return the sum of``// all natural numbers``static` `int` `sumNatural(``int` `n)``{``    ``int` `sum = (n * (n + ``1``)) / ``2``;``    ``return` `sum;``}` `// Function to return the sum``// of all numbers in range L and R``static` `int` `suminRange(``int` `l, ``int` `r)``{``    ``return` `sumNatural(r) - sumNatural(l - ``1``);``}` `// Driver Code``public` `static` `void` `main(String[] args)``{``    ``int` `l = ``2``, r = ``5``;``    ``System.out.println(``"Sum of Natural numbers from L to R is "``+suminRange(l, r));` `}``}``// This code is contributed by mits`

## Python3

 `# Python3 program to print the sum  of``# all numbers in range L and R` `# Function to return the sum of all natural numbers``def` `sumNatural(n):` `    ``sum` `=` `(n``*``(n``+``1``))``/``/``2` `    ``return` `sum` `# Function to return the sum``# of all numbers in range L and R``def` `suminRange(l, r):``    ``return` `sumNatural(r) ``-` `sumNatural(l``-``1``)` `#  Driver Code``l ``=``2``; r``=` `5``print``(``"Sum of Natural numbers 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 natural numbers``static` `int` `sumNatural(``int` `n)``{``    ``int` `sum = (n * (n + 1)) / 2;``    ``return` `sum;``}` `// Function to return the sum``// of all numbers in range L and R``static` `int` `suminRange(``int` `l, ``int` `r)``{``    ``return` `sumNatural(r) -``           ``sumNatural(l - 1);``}` `// Driver Code``static` `public` `void` `Main ()``{``    ``int` `l = 2, r = 5;``    ``Console.WriteLine(``"Sum of Natural numbers "` `+``                              ``"from L to R is "` `+``                               ``suminRange(l, r));``}``}` `// This code is contributed by akt_mit`

## PHP

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## Javascript

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Output:
`Sum of Natural numbers from L to R is 14`

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