public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int cases = sc . nextInt ( ) ;
  while ( cases > 0 ) {
    int n = sc . nextInt ( ) ;
    int m = sc . nextInt ( ) ;
    long min = Long . MAX_VALUE ;
    long sum = 0 ;
    long pos = 0 ;
    long neg = 0 ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      for ( int j = 0 ;
      j < m ;
      j ++ ) {
        long temp = sc . nextLong ( ) ;
        if ( temp > 0 ) {
          pos ++ ;
        }
        else {
          neg ++ ;
        }
        sum += Math . abs ( temp ) ;
        min = Math . min ( min , Math . abs ( temp ) ) ;
      }
    }
    if ( neg % 2 != 0 ) {
      sum -= 2 * min ;
    }
    System . out . println ( sum ) ;
    cases -- ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int cases = sc . nextInt ( ) ; while ( cases > 0 ) { int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; long min = Long . MAX_VALUE ; long sum = 0 ; long pos = 0 ; long neg = 0 ; for ( int i = 0 ; i < n ; i ++ ) { for ( int j = 0 ; j < m ; j ++ ) { long temp = sc . nextLong ( ) ; if ( temp > 0 ) { pos ++ ; } else { neg ++ ; } sum += Math . abs ( temp ) ; min = Math . min ( min , Math . abs ( temp ) ) ; } } if ( neg % 2 != 0 ) { sum -= 2 * min ; } System . out . println ( sum ) ; cases -- ; } }
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