public static int hourglassSum(List<List<int>> arr)
    {
        int sum=0;
        int max = 0;
        int f =1;
        for(var i=1; i<5;i++) {
             for(var j=1; j<5;j++) {
                sum = arr[i][j] + arr[i-1][j-1]+arr[i-1][j]+arr[i-1][j+1]
                +arr[i+1][j-1]+arr[i+1][j]+arr[i+1][j+1];
                if( f==1) {
                    max = sum;
                    f = 0;
                }
                
                if(max < sum) max = sum;
             }
        }
        return max;

    }