#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
using str = string;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;
using vi = vector<int>;
using vii = vector<pi>;
using vll = vector<pl>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vpi = vector<pi>;
using vpl = vector<pl>;
using vpd = vector<pd>;
const ll BIG = 998244353;
const double PI = 3.141592653589793238;
ll binpow(ll a, ll b, ll m) {
  ll res = 1;
  while (b > 0) {
    if (b & 1) {
      res = (res * a) % m;
    }
    b >>= 1;
    a = (a * a) % m;
  }
  return res;
}
template <typename T, typename Q>
T max(T a, Q b) {
  if (a > b) return a;
  return b;
}
template <typename T, typename Q>
T min(T a, Q b) {
  if (a < b) return a;
  return b;
}
ll fact[1000001];
void precal() {
  fact[0] = 1;
  fact[1] = 1;
  for (int i = 2; i <= 1e6; i++) {
    fact[i] = (fact[i - 1] * i) % BIG;
  }
}
ll mod(ll a) { return a % BIG; }
ll imod(ll a) { return binpow(a, BIG - 2, BIG); }
ll C(ll a, ll b) {
  return mod(fact[a] * mod(imod(fact[a - b]) * imod(fact[b])));
}
int n, m;
void solve() {
  cin >> n >> m;
  int arr[n][m];
  int sum = 0;
  int p = 0;
  int q = 1000;
  int r = 0;
  for (ll i = (0); i < (n); ++i) {
    for (ll j = (0); j < (m); ++j) {
      cin >> arr[i][j];
      if (arr[i][j] < 0) {
        p++;
      }
      q = min(abs(arr[i][j]), q);
      if (arr[i][j] == 0) {
        r = 1;
      }
      sum += abs(arr[i][j]);
    }
  }
  if ((p % 2) && (r == 0)) {
    sum -= 2 * q;
  }
  cout << sum;
  cout << "\n";
  ;
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
