import java.util.*;
public class Main {
static int n;
static int[][] dp = new int[500][500];
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
for (int i = 0; i < n; i++) {
for (int j = 0; j < i + 1; j++) {
dp[i][j] = sc.nextInt();
}
}
for (int i = 1; i < n; i++) {
for (int j = 0; j <= i; j++) {
int upLeft, up;
if (j == 0) upLeft = 0;
else upLeft = dp[i - 1][j - 1];
if (j == i) up = 0;
else up = dp[i - 1][j];
dp[i][j] = dp[i][j] + Math.max(upLeft, up);
}
}
int result = 0;
for (int i = 0; i < n; i++) {
result = Math.max(result, dp[n - 1][i]);
}
System.out.println(result);
}