Given an array of strings, find the 3 adjacent elements with the longest combined length. Return them in the form of an array.

Example

function combined(arr){
    // Find the 3 adjacent elements with longest combined length
}

combined(["this", "is", "an", "array"])
// Output:  ["is", "an", "array"]
    // they have the longest combined length of any 3 adjacent elements. (9 characters)
    // In contract, ["this", "is", "an"] only has a combined length of 8 characters