In this example we will show how to calculate the sum of N natural numbers.

### Source Code

```
#! /usr/bin/env python3
# -*- coding: utf-8 -*-
n = int(input("Enter a natural number: "))
sum1 = 0
for i in range(1, n+1):
sum1 += i
print("The sum of first n natural numbers is", sum1)
```

Output:

```
Enter a natural number: 10
The sum of first n natural numbers is 55
Enter a natural number: 55
The sum of first n natural numbers is 1540
```