#include<iostream>
#include<algorithm>
using namespace std;
#define MAX 101
int d[MAX][MAX];
int maxsum[MAX][MAX];int n;
int Maxsum(int i,int j)
{ if(maxsum[i][j]!=-1)
return maxsum[i][j];
if(i==n)
maxsum[i][j]=d[i][j];
else
{ int x=Maxsum(i+1,j);
int y=Maxsum(i+1,j+1);
maxsum[i][j]=max(x,y)+d[i][j];
}
return maxsum[i][j];
}
int main(){
int i,n,j;
cin>>n;
for(i=1;i<=n;i++)
for(j=1;j<=i;j++)
{cin>>d[i][j];
maxsum[i][j]=-1;
}
cout<<Maxsum(1,1)<<endl;
}