c three.f
c Three Card Game Paradox
c by Conor Gilmer
c
      program three
c variables
      integer stick, twist, games, outcome
      real stickpc, twistpc
      integer run
     
      stick = 0
      twist = 0
      games = 1000

      print *,"Three Card Game Paradox!"
      print *,"Play ", games, " Times"
c run the game games times
      do i=1, games
        outcome = run(i)
        if (outcome == 1) then
                stick = stick + 1
        else
                twist = twist + 1
        end if
      end do
c output the results
      twistpc = (real(twist)/real(games)) * 100
      stickpc = (real(stick)/real(games)) * 100
      print *,"Results:"
      print *,"Sticking wins ", stick, " times (",stickpc, " %)."
      print *,"Changing wins ", twist, " times (",twistpc, " %)."
      if (stick.le.twist) then
        print *,("Changing is better")
      else
        print *,("Sticking is better")
      endif
      print *,"The End!"
      end program three

c function to generate a simple random number between 1 and 3
c modulus means its numbers between 0 and 3 but if zero random again
      integer function simplerandom(x)
      integer x
      do
        simplerandom = mod(irand(),4)
c        print *,"simple random = ", simplerandom
        if (simplerandom.ne.0) exit
      end do
      return
      end function

c This is a function to play a game and return if stick or twisting won
      integer function run(x)
      integer x
      integer winning, chosen, remove
      character cards(3)
      integer simplerandom
      cards(1) = "A"
      cards(2) = "B"
      cards(3) = "C"
      
      winning = simplerandom(2)    
      remove = simplerandom(2)    
      chosen = simplerandom(1)    

      do
       remove = simplerandom(3)    
       if ((remove.ne.winning) .and. (remove.ne.chosen)) exit
      end do
      print *,"winning ",winning," chosen ",chosen, " card ",cards(2)

      if (winning.eq.chosen) then
        run = 1
      else
        run = 0
      endif
      RETURN 
      END