import java.util.*;
 
public class Main{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
 
        int n = sc.nextInt();
 
        int a[][] = new int[n][n];
        for(int i=0;i<n;i++){
            for(int j=0;j<n;j++){
                a[i][j] = sc.nextInt();
             }
        }
 
        int sum = 0;
 
        for(int i=0;i<n;i++){
 
                sum = sum + a[i][i] + a[i][n-i-1];
            }
 
 
        for(int j=0;j<n;j++){
           sum += a[n/2][j];
        }
        for(int i=0;i<n;i++){
           sum += a[i][n/2];
        }
 
        sum -=  3 * a[n/2][n/2];
 
    System.out.println(sum);
 
    }
}

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

MwoxIDIgMwo0IDUgNgo3IDggOQoK

3
1 2 3
4 5 6
7 8 9