#include<bits/stdc++.h>
using namespace std;
int main(){
    int i,j,n,a[10][10]={0},b[10][10]={0},k,x=0,s,m=0;
    scanf("%d",&n);
    for(i=1,j=1,k=0;;)
    {
        cin>>i>>j>>k;
        a[i][j]=k;
        if(i==0&&j==0&&k==0)
        	break;
    }
    b[0][0]=0;
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
        {    
            if(b[i][j-1]>b[i-1][j])
                b[i][j]=b[i][j-1]+a[i][j];
            else
                b[i][j]=b[i-1][j]+a[i][j];
        }
    m+=b[n][n];
    for(s=b[n][n];s!=0;)
        for(i=1;i<=n;i++)
            for(j=1;j<=n;j++)
                if(b[i][j]==s)
                {
                    s=b[i][j]-a[i][j];
                    a[i][j]=0;
                }
    b[0][0]=0;
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
        {    
            if(b[i][j-1]>b[i-1][j])
                b[i][j]=b[i][j-1]+a[i][j];
            else
                b[i][j]=b[i-1][j]+a[i][j];
        }
    m+=b[n][n];
    cout<<m; 
}