#include <bits/stdc++.h>

using namespace std;

ifstream in ("sumtri.in");
ofstream out ("sumtri.out");

int main()
{
    int n, i, j, tri[102][102];
    in>>n;
    for(i=1; i<=n; i++)
        for(j=1; j<=i; j++)
            in>>tri[i][j];
    for(i=n-1; i>=1; i--)
        for(j=1; j<=i; j++)
            tri[i][j]+=max(tri[i+1][j], tri[i+1][j+1]);
    out<<tri[1][1];
    return 0;
}