fata fw07p04; title 'CHAPTER 7, PROBLEM 4';
input X   Y;
cards;
   -1     7
   -1     3
   -1     6
   -1     6
   -1     7
   -1     4
   -1     2
    1     5
    1     8
    1    12
    1     8
    1     6
    1     8
    1     9