package Lab;

import java.util.Scanner;

public class Condensed_07 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        String[] input = scan.nextLine().split("\\s+");
        int[] numbers = new int[input.length];

        for (int i = 0; i < input.length; i++) {
            numbers[i] = Integer.parseInt(input[i]);
        }

        while (numbers.length > 1) {
            int[] condesed = new int[numbers.length-1];
            for (int i = 0; i < numbers.length-1; i++) {
                condesed[i] = numbers[i] + numbers[i + 1];
            }
            numbers = condesed;
        }
        System.out.println(numbers[0]);
    }
}