#include <iostream>
#include <vector>
using namespace std;
int main(){
	int n;
	cin >> n;
	vector<vector<int>> arr(n);
	vector<vector<int>> dp(n);
	int tmp;
	for(int i = 0; i < n; i++){
		for(int j = 0; j < i + 1; j++){
			cin >> tmp;
			arr[i].push_back(tmp);
			dp[i].push_back(-1);
		}
	}
	dp[0][0] = arr[0][0];
	for(int i = 1; i < n; i++){
		for(int j = 0; j < i + 1; j++){
			if(j == 0) dp[i][j] = dp[i - 1][j] + arr[i][j];
			else if(j == i) dp[i][j] = dp[i - 1][j - 1] + arr[i][j];
			else{
				dp[i][j] = max(dp[i - 1][j - 1] + arr[i][j], dp[i - 1][j] + arr[i][j]);
			} 
		}
	}
	int max = -2;
	for(int i = 0; i < n; i++){
		if(dp[n - 1][i] > max) max = dp[n - 1][i];
	}
	cout << max << endl;
	return 0;
}