system SumToN {
  const PARAM { N = 1; }
  typealias byte int wrap (0,255);
  
  byte x := 1;
  byte t1;
  byte t2;
	
  active thread Thread1() {
    loc loc0: 
      do { t1 := x; }
      goto loc1;

    loc loc1: 
      do { t2 := x; }
      goto loc2;
			
    loc loc2: 
      do { x := t1 + t2; }
      goto loc0;
  }
  
  active thread Thread2() {
    loc loc0: 
      do { t1 := x; }
      goto loc1;
			
    loc loc1: 
      do { t2 := x; }
      goto loc2;
			
    loc loc2: 
      do { x := t1 + t2; }
      goto loc0;
  }

  active thread Thread0() {
    loc loc0: 
      do { assert (x != (byte)PARAM.N); }
      return;
  }
}