#include<bits/stdc++.h>
using namespace std;
const int N = 1e4 + 10;
int r;
int a[N][N],dp[N][N];
int main(){
	
	cin >> r;
	for(int i = 1;i <= r;i++){
		for(int j = 1;j <= i;j++){
			cin >> a[i][j];
		}
	}
	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]) + a[i][j];
		}
	}
	int nmax = -1;
	for(int i = 1;i <= r;i++){
		nmax = max(nmax,dp[r][i]);
	}
	cout << nmax;
	return 0;
}