ZZ

package com.company;

import java.util.Scanner;

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

        String line = scanner.nextLine();
        String[] cord = line.split(" ");
        int[] dimentions = new int[cord.length];

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

        int rows = dimentions[0];

        int sum = 0;

        for (int i = 0; i < rows; i++) {
            String matrixRow = scanner.nextLine();
            String[] matrixRowArr = matrixRow.split(" ");
            int[] array = new int[matrixRowArr.length];
            for (int j = 0; j < array.length; j++) {
                array[j] = Integer.parseInt(matrixRowArr[j]);
            }
            if (i == 0) {
                for (int j = 0; j < array.length; j += 2) {
                    sum += array[j];
                }
            } else if (i == rows - 1) {
                if (i % 2 == 0) {
                    for (int j = 0; j < array.length; j += 2) {
                        sum += array[j];
                    }
                } else {
                    for (int j = 1; j < array.length; j += 2) {
                        sum += array[j];
                    }
                }
            } else {
                if (i % 2 == 0) {
                    for (int j = 2; j < array.length - 1; j += 2) {
                        sum += ((array[j]) * 2);
                    }
                    sum += ((array[0]));
                } else {
                    for (int j = 1; j < array.length - 1; j += 2) {
                        sum += ((array[j]) * 2);
                    }
                    sum += ((array[array.length - 1]));
                }
            }
        }
        System.out.println(sum);
    }
}