#include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       long long int n, m, i, j, zero = 0, neg = 0, tot = 0, val = INT_MIN,                                 val2 = INT_MAX;       cin >> n >> m;       long long int b[n][m];       for (i = 0; i < n; i++) {         for (j = 0; j < m; j++) {           cin >> b[i][j];           if (b[i][j] < 0) {             neg++;             if (neg == 1)               val = b[i][j];             else if (val < b[i][j])               val = b[i][j];           } else if (b[i][j] == 0)             zero++;           else             val2 = min(val2, b[i][j]);           tot += abs(b[i][j]);         }       }       if (neg % 2 == 0 || zero != 0)         cout << tot << endl;       else {         cout << tot + 2 * max(val, -val2) << endl;       }     }   }   