#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int n, ans;
int a[1005][1005];
//dp[i][j] 从(1,1)走到(i,j)位置和的最大值
int dp[1005][1005];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= i; j++)
            cin >> a[i][j];
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= i; j++)
            if (i == 1)
                dp[i][j] = a[i][j];
            else if (j == 1)
                dp[i][j] = dp[i - 1][j] + a[i][j];
            else if (j == i)
                dp[i][j] = dp[i - 1][j - 1] + a[i][j];
            else
                dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - 1]) + a[i][j];
    ans = -1;
    for (int j = 1; j <= n; j++)
        ans = max(ans, dp[n][j]);
    cout << ans << endl;
    return 0;
}