#include <iostream>
#include <map>
#include "queue"
#include <set>

int main() {
    int rows = 0;
    int cols = 0;
    std::cin >> rows;
    std::cin >> cols;
    std::map<std::pair<int, int>, int> map;
    int tmp;
    int sum = 0;
    for (int x = 0; x<rows; x++) {
        for (int y = 0; y<cols; y++) {
            std::cin >> tmp;
            sum += tmp;
            map.insert({{x, y}, tmp});
        }
    }
    if (rows%2 == 1 || cols%2==1) {
        std::cout << sum << std::endl;
    } else {
        int max = 0;
        int tmp = 0;
        for ( int i= 0; i< rows;i++){
            for (int j = 0; j < cols;j++) {
                if((j == 0 && i%2==0) ||( j == (cols-1) && i%2==1)){
                    continue;
                }else{
                    tmp += map.at({i,j});
                }
            }
            if (sum - tmp > max){
                max = sum - tmp;
            }
            tmp = 0;
        }
        for ( int j = 0; j < cols;j++){
            for (int i= 0; i< rows;i++) {
                if((i == 0 && j%2==0) || (i == (rows-1) && j%2==1)){
                    continue;
                }else{
                    tmp += map.at({i,j});
                }
            }
            if (sum - tmp > max){
                max = sum - tmp;
            }
            tmp = 0;
        }
        std::cout << max << std::endl;
    }
    return 0;
}