/*
  NAME : Nursoltan
  PROB : numtri
  LANG : C++
  DATE : 01/07/11 14:08
*/
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <sstream>
#include <iostream>
#include <map>
#include <set>
#include <stack>
#include <utility>
#include <queue>
 
using namespace std;
 
#define MAX 100
#define INF INT_MAX
#define eps (1e-9)
 
#define FOR(_i,_k,_n) for(int (_i)=(_k); (_i)<(_n); (_i)++)
#define FORR(_i,_k,_n) for(int (_i)=(_k); (_i)>=(_n); (_i)--)
#define CLR(_x) memset((_x),0,sizeof(_x))
#define SQR(_x) ((_x)*(_x))
#define all(_x) _x.begin(),_x.end()
#define sz(_x) sizeof(_x)
 
#define vc vector<int>
#define pb push_back
#define mp make_pair
#define iss istringstream
#define oss ostringstream
#define px first
#define py second
 
typedef long long ll;
typedef pair <int,int> point;
int ABS(int _x){ return _x>0?_x:-_x; }
 
int main()
{
    freopen("numtri.in","r",stdin);
    freopen("numtri.out","w",stdout);
 
    int n,a[1001][1001];
    cin>>n;
 
    FOR(i,0,n) FOR(j,0,i+1) cin>>a[i][j];
    FOR(i,1,n) a[i][0]+=a[i-1][0],a[i][i]+=a[i-1][i-1];
    FOR(i,2,n) FOR(j,1,i) a[i][j]+=max(a[i-1][j],a[i-1][j-1]);
 
    cout<<(*max_element(a[n-1],a[n-1]+n))<<endl;
 
    //system("pause");
    return 0;
}