Пятеричная система счисления

procedure ToFive(var x: string; p: integer);
var
  i, t: integer;
begin
  t := 0;
  for i := 1 to length(x) do t := t * p + ord(x[i]) - ord('0');
  x := '';
  repeat
    x := char(t mod 5 + ord('0')) + x;
    t := t div 5
  until t = 0
end;
 
var
  s, a: string;
  i, c: integer;
begin
  writeln('161(8)+34(7)-15(10) in the five');
  s := '161';
  write(s, '(8) = ');
  ToFive(s, 8);
  writeln(s, '(5)');
  a := '34';
  write(a, '(7) = ');
  ToFive(a, 7);
  writeln(a, '(5)');
  write(s, '(5) + ', a, '(5) = ');
  while length(a) < length(s) do a := '0' + a;
  c := 0;
  for i := length(s) downto 1 do
    begin
      inc(s[i], ord(a[i]) - ord('0') + c);
      if s[i] > '4' then
        begin
          c := 1;
          dec(s[i], 5)
        end
      else c := 0
    end;
  if c > 0 then s := '1' + s;
  writeln(s, '(5)');
  a := '15';
  write(a, '(10) = ');
  ToFive(a, 10);
  writeln(a, '(5)');
  write(s, '(5) - ', a, '(5) = ');
  while length(a) < length(s) do a := '0' + a;
  c := 0;
  for i := length(s) downto 1 do
    begin
      dec(s[i], ord(a[i]) - ord('0') + c);
      if s[i] < '0' then
        begin
          c := 1;
          inc(s[i], 5)
        end
      else c := 0;
    end;
  while s[1] = '0' do delete(s, 1, 1);
  writeln(s, '(5)');
  readln
end.