import java.util.Scanner;

 public class Main{
	 public static void main(String[] args) {
		 Scanner sc=new Scanner(System.in);
		 int n=sc.nextInt();
		 int dp[][]=new int[n+1][n+1];

         int max=0;
		 for(int i=1;i<=n;i++)
			 for(int j=1;j<=i;j++) {
				 dp[i][j]=sc.nextInt();
				 dp[i][j]=Math.max(dp[i][j]+dp[i-1][j-1],dp[i][j]+dp[i-1][j]);
				 if(i==n&&dp[n][j]>max) {
					 max=dp[n][j];
				 }
			 }

		 System.out.println(max);		 
	 }
 }