#include <stdio.h>
#include <malloc.h>
#define ERROR -1
#define OK 0
int main (){
int n, i, j, sum;
sum = 0;
scanf("%d", &n);
if(n <= 0){
printf("0\n");
return ERROR;
}else if(n == 1) {
scanf("%d", &sum);
printf("%d\n", sum);
return OK;
}else{
int **arr = (int **)malloc(n*sizeof(int *));
for(i = 0; i < n; i++) {
arr[i] = (int *)malloc(n*sizeof(short int));
}
for(i = 0; i < n; i++) {
for(j = 0; j < n; j++) {
scanf("%d", &arr[i][j]);
}
}
for(i = 0; i < n; i++) {
for(j = 0; j < n; j++) {
if(i == 0|| i == n-1|| j == 0|| j == n-1) {
sum += arr[i][j];
}
}
}
printf("%d\n",sum);
for (i = 0; i < n; i++) {
if(arr[i] != NULL){
free(arr[i]);
}
}
if(arr != NULL){
free(arr);
}
return OK;
}
return 0;
}