## Example 1: Find sum of natural numbers without formula

```
# take input from the user
num = as.integer(readline(prompt = "Enter a number: "))
if(num 0) {
sum = sum + num
num = num - 1
}
print(paste("The sum is", sum))
}
```

**Output**

Enter a number: 10 [1] "The sum is 55"

Here, we ask the user for a number and display the sum of natural numbers upto that number.

We use `while`

loop to iterate until the number becomes zero. On each iteration, we add the number
`num` to `sum`, which gives the total sum in the end.

We could have solved the above problem without using any loops using a formula.

From mathematics, we know that sum of natural numbers is given by

n*(n+1)/2

For example, if n = 10, the sum would be (10*11)/2 = 55.

## Example 2: Find sum of natural numbers using a formula

```
# take input from the user
num = as.integer(readline(prompt = "Enter a number: "))
if(num
```

**Output**

Enter a number: 10 [1] "The sum is 55"