#include <bits/stdc++.h>
using namespace std;
ifstream fin ("sumtri.in");
ofstream fout ("sumtri.out");
int a[105][105], c[105][105], d[105][105],n,t[105][105];
int main()
{
    int i,j;
    fin>>n;
    for(i=1;i<=n;i++)
        for(j=1;j<=i;j++)
        fin>>t[i][j];
    for(j=1;j<=n;j++)
        c[n][j]=t[n][j];
    for(i=n-1;i>=1;i--)
        for(j=1;j<=i;j++)
        if(c[i+1][j]>c[i+1][j+1])
    {
        c[i][j]=t[i][j]+c[i+1][j];
        d[i][j]=j;
    }
    else
    {
        c[i][j]=t[i][j]+c[i+1][j+1];
        d[i][j]=j+1;
    }
    fout<<c[1][1]<<endl;
    return 0;
}