#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;

int main()
{
    freopen("flip.in", "r", stdin);
    freopen("flip.out", "w", stdout);
    int n, m;
    cin >> n >> m;
    vector<vector<int>> x(n, vector<int>(m));
    for (int i = 0; i < n; ++i) {
        for(int j = 0; j < m; ++j)
            cin >> x[i][j];
    }
    for(int i = 0; i < n; ++i) {
        int sum = 0;
        for(int j = 0; j < m; ++j)
            sum += x[i][j];
        if (sum < 0) {
            for(int j = 0; j < m; ++j)
               x[i][j] *= -1;
        }
    }
    for(int j = 0; j < m; ++j) {
        int sum = 0;
        for(int i = 0; i < n; ++i)
            sum += x[i][j];
        if (sum < 0) {
            for(int i = 0; i < n; ++i)
               x[i][j] *= -1;
        }
    }
    long long sum = 0;
    for(int i = 0; i < n; ++i) {
        for(int j = 0; j < m; ++j)
            sum += x[i][j];
    }
    cout << sum;
    return 0;
}