subroutine sub1(first, second, third, out, res)
      real first, second, third, out, res
c start mixing all variables :
      out = first*second + 3.0*third
      res = sin(first) + cos(second)
      first = 2.0 * first
      third = 2.0/second
c now overwrite some values...
      if (first.gt.second) then
         first = cos(out)
         second = F(out)
      else
c ...in one or in all cases
         first = exp(out)
         second = G(out)
      endif
      end