3 while n > 1 do {

     3 while n > 1 do {

     4   if n % 2 == 0 

     4   if n % 2 == 0 

     5   then n := n/2 

     5   then n := n/2 

     6   else n := 3*n+1

     6   else n := 3*n+1

     7 };

     7 };