#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
int M, N;
int sum_col = 0, sum_row = 0, sum = 0;
int **A;
ifstream ifile ("flip.in");
ofstream ofile ("flip.out");
ifile >> N;
ifile >> M;
A = new int*[N];
for (int i = 0; i < N; i++)
A[i] = new int [M];
for (int i = 0; i < N; i++)
for (int j = 0; j < M; j++)
ifile >> A[i][j];
for (int i = 0; i < N; i++)
{
for (int j = 0; j < M; j++)
{
sum_row = sum_row + A[i][j];
}
if (sum_row < 0)
{
for (int j = 0; j < M; j++)
{
A[i][j] = (-1)*A[i][j];
}
}
sum_row = 0;
}
for (int i = 0; i < M; i++)
{
for (int j = 0; j < N; j++)
{
sum_col = sum_col + A[j][i];
}
if (sum_col < 0)
{
for (int j = 0; j < N; j++)
{
A[j][i] = (-1)*A[j][i];
}
sum = sum - sum_col;
}
else
sum = sum + sum_col;
sum_col = 0;
}
ofile << sum;
}