With a little massaging of input and output you can convert any program P into the program P_n defined as "repeat P n times". For any n P terminate if and only

With a little massaging of input and output you can convert any program P into the program P_n defined as "repeat P n times". For any n P terminate if and only if P_n terminates, so no general procedure can decide the halting problem for all programs except 1.