function hourglassSum(arr) {
    let largestSum = NaN
    const [hgHeight, hgWidth] = [3, 3]
    
    for (let row = 0; row <= hgHeight; row++) {
        for (let j = 0; j <= hgWidth; j++) {
            let sum = 0
            
            for (let c = 0; c < hgWidth; c++) {
                sum += arr[row][c+j] + arr[row+2][c+j]
                if (c == 1) {
                    sum += arr[row+1][c+j]
                }   
            }
            
            if (isNaN(largestSum) || sum > largestSum) {
                largestSum = sum
            }
        }
    }
    return largestSum;
}