func hg_sum(x int, y int, mat [][]int) int {
var sum int
sum += (mat[y-1][x-1] + mat[y-1][x] + mat[y+1][x-1])
sum += mat[y][x]
sum += (mat[y-1][x+1] + mat[y+1][x] + mat[y+1][x+1])
return sum
}
func maxSum(grid [][]int) int {
var max int
for i:=1; i<len(grid)-1; i++ {
for j:=1; j<len(grid[0])-1; j++ {
sum := hg_sum(j, i, grid)
if sum > max {
max = sum
}
}
}
return max
}