def hourglassSum(arr):
    
    result=None
    n=len(arr)-2
    for i in range(n):
        for j in range(n):
            hrglass_sum=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]
            if result is None:
                result=hrglass_sum
            
            elif hrglass_sum>result:
                result=hrglass_sum
    return result