# A Python program to add first n natural numbers

In this post i am writing a python program that prints** the sum of first n natural numbers**. We know that 1,2,3 … n are the natural numbers. With the following program the sum of first n natural numbers are calculated as:

Let a natural number be **5**. The first **n** natural numbers of 5 are 1,2,3,4 and 5. Then their **sum** is **1+2+3+4+5=15.**

**The following is the formula to evaluate the sum of first n natural numbers.**

1+ 2+ … + n = n(n+1) / 2 |

**Program**

**Output**

Enter a number 26
The sum of first 26 natural number is 351 |

**Explanation**

A natural number is given as input and is stored in a ‘**num**’ variable. The **sum** is initialized to 0 and **counter(i)** is set to 1(since 0+1=1). By using while loop we can check the condition whether the **counter(i)** is less than or equal to the input number(**num**). If the condition is true then the **sum** is added with the counter value **i** and the counter value of **i** increments by 1.This iteration continues till the condition becomes false and finally prints the **sum**.

By using for loops also we can print the sum of first n natural numbers. Here we go.

**Output**

Enter a number = 6
Sum of first 6 natural numbers is: 21 |