The positive numbers 1, 2, 3... are known as natural numbers and its sum is the result of all numbers starting from 1 to the given number.

For n, the sum of natural numbers is:

1 + 2 + 3 + ... + n

## Example 1: Sum of Natural Numbers using for loop

```
fun main(args: Array<String>) {
val num = 100
var sum = 0
for (i in 1..num) {
// sum = sum+i;
sum += i
}
println("Sum = $sum")
}
```

When you run the program, the output will be:

Sum = 5050

The above program loops from 1 to the given `num`(100) and adds all numbers to the variable `sum`.

Unlike Java, in Kotlin, you can use *ranges* (`1..num`

) and *in* operator to loop through numbers between 1 to `num`.

Here's the equivalent Java code: Java Program to Calculate the Sum of Natural Numbers

You can also use while loop to solve this problem as follows:

## Example 2: Sum of Natural Numbers using while loop

```
fun main(args: Array<String>) {
val num = 50
var i = 1
var sum = 0
while (i <= num) {
sum += i
i++
}
println("Sum = $sum")
}
```

When you run the program, the output will be:

Sum = 1275

In the above program, unlike a for loop, we have to increment the value of `i` inside the body of the loop.

Though both programs are technically correct, it is better to use for loop in this case. It's because the number of iteration (upto `num`) is known.

Visit this page to learn *how to find the sum of natural number using recursion*.