# 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

My Personal Notes arrow_drop_up

Just another competitive programmer

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.