func hourglassSum(arr: [[Int]]) -> Int {
    // Write your code here
        var maxSum: Int?
        for rowIndex in 1..<5 {
            for elementIndex in 1..<5 {
                let upperRow = arr[rowIndex-1]
                let currentRow = arr[rowIndex]
                let lowerRow = arr[rowIndex+1]
                let sum = upperRow[elementIndex-1] + upperRow[elementIndex] + upperRow[elementIndex+1] + currentRow[elementIndex] + lowerRow[elementIndex-1] + lowerRow[elementIndex] + lowerRow[elementIndex+1]
                if maxSum == nil {
                    maxSum = sum
                } else if let maxSumLocal = maxSum, maxSumLocal < sum {
                    maxSum = sum
                } else {
                    continue
                }
            }
        }
        return maxSum ?? 0
}