import java.util.Scanner;

public class Main {
	static int dp[][];
	static int tri[][];
	static int n;
	static int max;

	@SuppressWarnings("resource")
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);

		n = sc.nextInt();
		tri = new int[n + 1][n + 1];
		dp = new int[n + 1][n + 1];

		for (int i = 1; i < n + 1; i++) {
			for (int j = 1; j < i + 1; j++) {
				tri[i][j] = sc.nextInt();
				dp[i][j] = tri[i][j];
			}
		}

		run();

		System.out.println(max);
	}

	static void run() {
		for (int i = 1; i < n + 1; i++) {
			for (int j = 1; j < n + 1; j++) {
				if (dp[i - 1][j - 1] > dp[i - 1][j]) {
					dp[i][j] += dp[i - 1][j - 1];
				} else {
					dp[i][j] += dp[i - 1][j];
				}
				if (max < dp[i][j]) {
					max = dp[i][j];
				}
			}
		}
	}
}