#include <iostream>
#include <stdio.h>
using namespace std;
int map[1010][1010];
int time[1010][1010];
int main()
{
int n;
scanf("%d",&n);
for(int i=1;i<=n;i++)
for(int j=1;j<=i;j++)
scanf("%d",&map[i][j]);

time[1][1]=map[1][1];
for(int i=2;i<=n;i++)
{
for(int j=2;j<i;j++)
time[i][j]=min(time[i-1][j],time[i-1][j-1])+map[i][j];
time[i][1]=min(time[i-1][1],time[i-1][i-1])+map[i][1];
time[i][i]=min(time[i-1][i-1],time[i-1][1])+map[i][i];

for(int k=i-1;k>0;k--)
time[i][k]=min(time[i][k],time[i][k+1]+map[i][k]);
time[i][i]=min(time[i][i],time[i][1]+map[i][i]);

for(int l=2;l<=i;l++)
time[i][l]=min(time[i][l],time[i][l-1]+map[i][l]);
time[i][1]=min(time[i][1],time[i][i]+map[i][1]);

for(int k=i-1;k>0;k--)
time[i][k]=min(time[i][k],time[i][k+1]+map[i][k]);
time[i][i]=min(time[i][i],time[i][1]+map[i][i]);

for(int l=2;l<=i;l++)
time[i][l]=min(time[i][l],time[i][l-1]+map[i][l]);
time[i][1]=min(time[i][1],time[i][i]+map[i][1]);
}
printf("%d",time[n][1]);
}