#include <bits/stdc++.h>
using namespace std;

int main()
{
    int t;
    cin >> t;
    for (int _ = 0; _ < t; _++)
    {
        int n, m;
        cin >> n >> m;
        vector<vector<int>> a(n, vector<int>(m, 0));
        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                cin >> a[i][j];
            }
        }

        int count = 0, zero = 0, sum = 0, am = 101;
        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                if(a[i][j] < 0) count++;
                else if(a[i][j] == 0) zero = 1;

                if(abs(a[i][j]) < am) am = abs(a[i][j]);
                sum += abs(a[i][j]);
            }
        }

        if(count % 2 == 0 || (count + zero) % 2 == 0)
        {
            cout << sum << endl;
        }
        else
        {
            cout << sum - 2 * am << endl;
        }
    }
    return 0;
}