#include <stdio.h>
int N, arr[2230][2230], tab[2230][2230];
void upd(int x, int y)
{
int m = 2147483647;
if(x > 1)
{
if(arr[y][x] < arr[y][x-1])
{
if(tab[y][x-1] < m) m = tab[y][x-1];
}
else
{
if(tab[y][x-1] + arr[y][x] - arr[y][x-1] + 1 < m) m = tab[y][x-1] + arr[y][x] - arr[y][x-1] + 1;
}
}
if(y > 1)
{
if(arr[y][x] < arr[y-1][x])
{
if(tab[y-1][x] < m) m = tab[y-1][x];
}
else
{
if(tab[y-1][x] + arr[y][x] - arr[y-1][x] + 1 < m) m = tab[y-1][x] + arr[y][x] - arr[y-1][x] + 1;
}
}
tab[y][x] = m;
}
int main()
{
//freopen("input.txt", "r", stdin);
int i, j;
scanf("%d", &N);
for(i = 1; i <= N; i ++) for(j = 1; j <= N; j ++) scanf("%d", &arr[i][j]);
for(i = 2; i <= N; i ++)
{
int x, y;
for(x = 1, y = i; x <= i; x ++, y --)
{
upd(x, y);
}
}
for(i = 2; i <= N; i ++)
{
int x, y;
for(x = i, y = N; x <= N; x ++, y --)
{
upd(x, y);
}
}
printf("%d", tab[N][N]);
return 0;
}
