start := 1000;
x := start;
y := start;
z := start;
while 0 < x do {
 while 0 < y do {
  while 0 < z do {
    z := z - 1
  };
  z := start;
  y := y - 1
 };     
 y := start;
 x := x - 1
};
write x;
write y;
write z