// matyconn.tc - 4/6,9-11/17 4/5,7/19 - tct
// ref: http://primepuzzle.com/tunxis/matyconn.html

valid int heads,total,claim [
 return ((heads!=7)*(total==claim)+(heads==7)*(total!=claim))
 ]

main [
 pl "matyconn.tc - 4/7/19 - tct"
 int b,r,g,y,head_count // blue,red,green,yellow

// do an exhaustive search

 b=6
 while b<=8 [
  r=6
  while r<=8 [
   g=6
   while g<=8 [
    y=6
    while y<=8 [
     head_count=b+r+g+y // total the heads
     // every dragon must be a liar and give the wrong total head count or
     // tell the truth and give the right total head count
     if (valid(b,head_count,28)) [
      if (valid(r,head_count,26)) [
       if (valid(g,head_count,27)) [
        if (valid(y,head_count,25)) [
         pl ""
         pl "There are";pn head_count;ps " total heads."
         pl ""
         pl "The blue dragon has";pn b;ps " heads."
         pl "The red dragon has";pn r;ps " heads."
         pl "The green dragon has";pn g;ps " heads."
         pl "The yellow dragon has";pn y;ps " heads."
         pl ""
         ]
        ]
       ]
      ]
      y=y+1
     ]
     g=g+1
    ]
    r=r+1
   ]
   b=b+1
  ]
 pl ""
 ]