#1010_Number Triangles

import java.util.Scanner;

/**
 * Created by mingy on 2016/3/22.
 */
 //这次就全是自己写的了，什么都没有参考，一次就很AC了很愉悦，用DP挺简单的
public class Quiz {
    public static int maxOfArray(int[] a) {
        int max = a[0];
        for (int i = 0; i < a.length; ++i)
            if (max < a[i])
                max = a[i];
        return max;
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        final int n = input.nextInt();
        int[][] x = new int[n + 2][n + 2];
        int[][] f = new int[n + 2][n + 2];

        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= i; ++j)
                x[i][j] = input.nextInt();

        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= i; ++j)
                f[i][j] = x[i][j];

        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= i; ++j) {
                f[i][j] = x[i][j] + Math.max(f[i - 1][j], f[i - 1][j - 1]);
            }
        }

        System.out.print(maxOfArray(f[n]));
       /* for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= n; ++j)
                System.out.print(f[i][j] + " ");
            System.out.println();
        }*/
    }
}