import java.util.Scanner;
//线性dp
//下标从0开始还是从1开始，看看如果有i-1就从1开始
public class Main {
    static int N = 510;
    static int[][] a = new int[N][N],f = new int[N][N];
    static int INF = 0x3f3f3f3f;
    public static void main(String[] arg)
    {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=i;j++)
            {
                a[i][j] = sc.nextInt();
            }
        }
        for(int i=0;i<=n;i++)//初始化，注意边界
        {
            for(int j=0;j<=i+1;j++)
                f[i][j] = -INF;
        }

        f[1][1] = a[1][1];

        for(int i=2;i<=n;i++)//i从2开始
        {
            for(int j=1;j<=i;j++)
            {
                f[i][j] = Math.max(f[i-1][j-1]+a[i][j],f[i-1][j]+a[i][j]);
            }
        }

        int res = -INF;
        for(int i=1;i<=n;i++)//最后一行遍历最大值
            res = Math.max(res,f[n][i]);
        System.out.println(res);
    }
}