#include <iostream>
    #include <algorithm>
    #include <vector>
    #include <cmath>


int main(){

    unsigned long long N, M;

    std::cin >> N >> M;

    unsigned long long minimum = INT64_MAX;
    unsigned long long  sum = 0;
    
    for(unsigned long long y = 0; y < N; y++){
        for(unsigned long long x = 0; x < M; x++){

            unsigned long long value;
            std::cin >> value;
            sum += value;
            if(y % 2 == 0){
                if(x % 2 == 1){
                    minimum = std::min(minimum, value);

                    //printf("%lld %lld\n", y, x);
                }
            }
            else{
                if(x % 2 == 0){
                    minimum = std::min(minimum, value);
                    //printf("%lld %lld\n", y, x);
                }
            }
        }
    }

    //std::cout << "sum: " << sum << std::endl;
    //std::cout << "minimum: " << minimum << std::endl;

    if(N % 2 == 1 || M % 2 == 1){
        std::cout << sum;
    }
    else{
        std::cout << sum - minimum;
    }

    return 0;
}