import java.util.Scanner;

//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int M = sc.nextInt();
        int min = Integer.MAX_VALUE;
        int count = 0;
        int[][] arr = new int[N][M];
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                arr[i][j] = sc.nextInt();
                count+=arr[i][j];
                if (!(i == 0 && j == 0) && !(i == N -1 && j == M - 1)) {
                    min = min > arr[i][j] ? arr[i][j] : min;
                }
            }
        }
        if (N % 2 == 0 && M % 2 == 0) {
            count -= min;
        }
        System.out.println(count);
    }
}