// http://prologin.org/training/challenge/demi2008/pathfinder
#include <stdio.h>
#include <stdlib.h>

#define MAX(x,y) ((x>y)?x:y)

int main()
{
  int n = 0;
  scanf("%d\n", &n);

  unsigned **map = (unsigned int **)malloc(n*sizeof(unsigned int *));
  unsigned **path = (unsigned int **)malloc(n*sizeof(unsigned int *));
  for(int i = 0; i < n; i++)
  {
    map[i] = (unsigned int *)malloc(n*sizeof(unsigned int));
    path[i] = (unsigned int *)malloc(n*sizeof(unsigned int));
  }

  for(int i = 0; i < n; i++)
    for(int j = 0; j < n; j++)
      scanf("%u", &map[i][j]);

  for(int i = 0; i < n; i++)
    for(int j = 0; j < n; j++)
      path[i][j] = 0;

  // Programmation dynamique
  path[0][0] = map[0][0];
  path[0][1] = path[0][0] + map[0][1];
  path[1][0] = path[0][0] + map[1][0];

  for(int i = 1; i < n; i++)
    for(int j = 1; j < n; j++)
      path[i][j] = map[i][j] + MAX(path[i-1][j], path[i][j-1]);

  printf("%u\n", path[n-1][n-1]);

  for(int i = 0; i < n; i++)
  {
    free(map[i]); map[i] = NULL;
    free(path[i]); path[i] = NULL;
  }
  free(map); map = NULL;
  free(path); path = NULL;

  return 0;
} // main()