Function that return the coordinates of the fourth vertex of the rectangle
static Pair < int , int > findFourthVertex ( int n , int m , String [ ] s ) { Dictionary < int , int > row = new Dictionary < int , int > ( ) ; Dictionary < int , int > col = new Dictionary < int , int > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { for ( int j = 0 ; j < m ; j ++ ) {