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# collections and control flow

Now that we have the while loop set up, it's time to compute the sum! Using the value of counter as an index value, retrieve each value from the array and add it to the value of sum.

For example: sum = sum + newValue. Or you could use the compound addition operator sum += newValue where newValue is the value retrieved from the array.

loops.swift
```let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

numbers.count
while counter < numbers.count
{
print(numbers[counter])
counter += 1
}

var newValue = numbers[newValue]
sum = sum + newValue
```

Below is the code which is incomplete: let numbers = [2,8,1,16,4,3,9] var sum = 0 var counter = 0

// Enter your code below numbers.count while counter < numbers.count { print(numbers[counter]) counter += 1 }

Hi,

You almost got it. You need to move the computing of the sum part inside of the while loop like I did below. var newValue will be 2 at first Then the sum computation will be sum = 0 + 2 So sum will be 2 Then increase the counter by 1 Then keep going - newValue will be 8 sum = 2 + 8 Increase counter by 1 And so on until you reach the end of the array.

```let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0