#include <bits/stdc++.h>
using namespace std;
 
void solve(){
	int n,m;
	cin>>n>>m;
 
	vector<vector<int>> v(n, vector<int>(m));
	long long x = 0;
	int cnt =0;
	int minn = INT_MAX;
	//  vector<vector<int>> matrix(rows, vector<int>(cols)); // 2D vector initialization
 
	for(int i =0;i<n;i++){
		for(int j=0;j<m;j++){
			cin>>v[i][j];
 
			x=x+abs(v[i][j]);
			if(v[i][j]<0) cnt++;// count all the negatives
 
			minn = min(minn, abs(v[i][j]));
 
		}
	}
 
	if(cnt%2 == 0){
		cout<<x<<endl;
	}else{
		cout<<x -(2*minn)<<endl;
	}
}
 
 
 
 
int main() {
	int t;cin>>t;
	while(t--){
		solve();
	}
	return 0;
}

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5
2 2
-1 1
1 1
3 4
0 -1 -2 -3
-1 -2 -3 -4
-2 -3 -4 -5
2 3
27 -66 -13
52 -56 -40
7 3
-6 1 -4
-84 -39 12
-55 34 -77
54 -100 -3
-58 50 37
16 68 78
-38 -36 87
4 2
-50 -21
-16 -7
86 76
62 -43