#include <bits/stdc++.h>   using namespace std;   void main2() {     long long int n, m, sum = 0, t = INT_MAX, temp, r = 0;     cin >> n >> m;     for (long long int i = 0; i < n; i++) {       for (long long int j = 0; j < m; j++) {         cin >> temp;         if (temp < 0) r++;         sum += abs(temp);         t = min(t, abs(temp));       }     }     if (r % 2 == 0)       cout << sum <<   n ;     else       cout << sum - 2 * t <<   n ;     return;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     long long int t = 1;     cin >> t;     while (t--) {       main2();     }     return 0;   }   