program dec_bin_oct;

const po2:array[0..7] of byte=(1,2,4,8,16,32,64,128); {powers of 2}
      bin:array[false..true] of char='01';
      oct:array[0..7] of char='01234567';

{Decimal to binary}
function dec2bin(b:byte):string;
 var s:string;
     i:byte;
 begin
  s:='';
  for i:=7 downto 0 do
   s:=s+bin[(po2[i] and b=po2[i])];
  dec2bin:=s;
 end;

{Binary ot decimal}
function bin2dec(s:string):byte;
 var l:byte absolute s; {lenght of s}
     i,b:byte;
 begin
  b:=0;
  while l<8 do s:=bin[false]+s;
  if l>8 then s:=copy(s,l-7,8);
  for i:=1 to l do
  if s[i]=bin[true] then b:=b+po2[8-i];
  bin2dec:=b;
 end;

{Binary to octal}
function bin2oct(b:string):string;
 var s:string;
     l:byte absolute b; {lenght of b}
     i:byte;
 begin
  while ((l mod 3)<>0) do b:=bin[false]+b;
  s:='';
  for i:=1 to (l div 3) do
   s:=s+oct[bin2dec(b[pred(i)*3+1]+b[pred(i)*3+2]+b[pred(i)*3+3])];
  bin2oct:=s;
 end;

{Octal to binary}
function oct2bin(b:string):string;
 var l:byte absolute b;
     i:byte;
     s:string;
 begin
  s:='';
  for i:=1 to l do
   s:=s+copy(dec2bin(ord(b[i])-48),6,3);
  oct2bin:=s;
 end;


var n:byte;

begin
 write(#13#10,'Enter a decimal :');readln(n);
 writeln(n,' in binary :',dec2bin(n),', in decimal :',bin2dec(dec2bin(n)));
 writeln(n,' in octal :',bin2oct(dec2bin(n)),' in binary: ',oct2bin(bin2oct(dec2bin(n))));
 readln;
end.