/*
ID:kevin_s1
PROG:numtri
LANG:C++
*/
#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <cstdlib>
#include <list>
#include <cmath>
using namespace std;
#define MAXN 1001
//gobal variable====
int R;
int tri[MAXN][MAXN];
int dp[MAXN][MAXN];
//==================
//dp[i][j] = max(dp[i - 1][j - 1], dp[i - 1][j]) + tri[i][j]
//function==========
//==================
int main(){
freopen("numtri.in","r",stdin);
freopen("numtri.out","w",stdout);
memset(dp,0,sizeof(dp));
memset(tri,0,sizeof(tri));
cin>>R;
for(int i = 1; i <= R; i++){
for(int j = 1; j <= i; j++){
cin>>tri[i][j];
}
}
dp[1][1] = tri[1][1];
for(int i = 1; i <= R; i++){
for(int j = 1; j <= i; j++){
dp[i][j] = max(dp[i - 1][j - 1], dp[i - 1][j]) + tri[i][j];
}
}
int maxnum = 0;
for(int i = 1; i <= R; i++){
if(dp[R][i] > maxnum )
maxnum = dp[R][i];
}
cout<<maxnum<<endl;
return 0;
}