var sum = [];
    
    for (i = 0; i < arr.length - 2; i++) {
        for (j =0; j < arr.length - 2; j++) {
            sum.push(arr[i][j]+arr[i][j+1]+arr[i][j+2]+arr[i+1][j+1]+arr[i+2][j]+arr[i+2][j+1]+arr[i+2][j+2]);
        }
    }
    
    console.log(Math.max(...sum));