#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;
long long calcSum(vector<vector<int>> x) {
    long long sum = 0;
    for(int i = 0; i < x.size(); ++i) {
        for(int j = 0; j < x[i].size(); ++j)
            sum += x[i][j];
    }
    return sum;
}
void reverseLine(vector<vector<int>> &x, int line) {
    for(int j = 0; j < x[line].size(); ++j)
        x[line][j] *= -1;
}
void reverseCol(vector<vector<int>> &x, int col) {
    for(int i = 0; i < x.size(); ++i)
        x[i][col] *= -1;
}
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)
            reverseLine(x, i);
    }
    for(int j = 0; j < m; ++j) {
        int sum = 0;
        for(int i = 0; i < n; ++i)
            sum += x[i][j];
        if(sum < 0)
            reverseCol(x, j);
    }
    cout << calcSum(x);
    return 0;
}