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# Sum of all natural numbers in range L to R

• Last Updated : 27 Aug, 2022

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`

Time Complexity: O(1)

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

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