import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Problem_18 {
 private static int heightOfTree = 100;
 private final String fileName = "problem_67.in";
 private int[][] tree;

 public int maxValue() throws IOException {
  readTree();

  for (int i = Problem_18.heightOfTree - 2; i >= 0; i--)
   for (int j = 0; j <= i; j++)
    tree[i][j] += tree[i + 1][j] > tree[i + 1][j + 1] ? tree[i + 1][j] : tree[i + 1][j + 1];

  return tree[0][0];
 }

 private void readTree() throws IOException {
  tree = new int[Problem_18.heightOfTree][];

  BufferedReader bufferedReader = new BufferedReader(new FileReader(fileName));
  for (int i = 0; i < Problem_18.heightOfTree; i++) {
   tree[i] = new int[i + 1];
   String[] values = bufferedReader.readLine().split(" ");
   for (int j = 0; j <= i; j++)
    tree[i][j] = Integer.parseInt(values[j]);
  }
 }

 public static void main(String[] args) throws IOException {
  System.out.println(new Problem_18().maxValue());
 }
}