# Sum of all natural numbers in range L to R

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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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

 ` `

Output:

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

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.