program c7p1
      implicit none
      real x1,x2,x3,y1,y2,y3,dot,z
      x1 = 1
      x2 = 2
      x3 = 3
      y1 = 4
      y2 = 5
      y3 = 6
      z = 2
      print *, z
      print *, dot(x1,x2,x3,y1,y2,y3)
      print *, z
      end

      real function dot(x1,x2,x3,y1,y2,y3,z)
      real z
      z = 16
      print *, z
      dot = x1*y1+x2*y2+x3*y3
      return
      end