var
  remain: array[2..36]of longint;
  p: char;
  i, num, max: integer;
begin
  fillchar(remain, sizeof(remain), 0);
  max := 0;
  while not eof do
  begin
    read(p);
    if p in ['0'..'9'] then num := ord(p) - 48 else
    if p in ['A'..'Z'] then num := ord(p) - ord('A') + 10
    else continue;
    if num > max then max := num;
    for i := 2 to 36 do
    remain[i] := (remain[i] * i + num) mod (i - 1);
  end;
  for i := max + 1 to 36 do
  if remain[i] = 0 then
  break;
  if remain[i] = 0 then
  writeln(i) else writeln('No solution.');
end.

"if p in ['0'..'9'] then num := ord(p) - 48 else"

I think it is
if p in ['0'..'9'] then num := (ord(p) - 48) mod 10 else