Here is the perfect land whose sum value is maximum.

Note: Before going to solution please try it by yourself.

C++ implementation:

#include <bits/stdc++.h>
#define FASTIO ios_base::sync_with_stdio(false); cin.tie(NULL)

using namespace std;
int main()
{
	FASTIO; //Taking Fast Input Output
	int n,m,x;
	cin>>n>>m;      //taking input n and m
	
	int arr[n][m];
	for(int i=0;i<n;i++)
	{
		for(int j=0;j<m;j++)
		{
			//taking input for the matrix
			cin>>arr[i][j];
		}
	}
	
	//it will store the maximum value of the perfect land
	int max1=0;
	for(int i=0;i<n-2;i++)
	{
		for(int j=0;j<m-2;j++)
		{
			//it will calclute the total sum of each C shape land
			int sum1=0;
			//here we are calculating the sum of each C shape 
			//land of size 3*3
			//this is for first line of C shape
			sum1=sum1+arr[i][j]+arr[i][j+1]+arr[i][j+2]; 
			//second line of C shape
			sum1+=arr[i+1][j];
			//3rd line of C shape
			sum1+=arr[i+2][j]+arr[i+2][j+1]+arr[i+2][j+2]; 

			//checking if the sum is grater than 
			//the previous C shape land
			if(sum1>=max1)
				max1=sum1;
		}
	}
	cout<<max1<<"\n";

	return 0;
}

Output