Const
 F0name = 'myfile.txt';
 Fname = 'tmp.txt';
type myfile = file of char;
Var f0,f : myfile;
 Ch : Char;
Begin
 Assign(f,Fname);
 Assign(f0,F0name);
 Reset(f0);
 ReWrite(f);
 While not EOF(f0) do
 Begin
   Read(f0,Ch);
   If (Ch>='0') and (Ch<='9') then Write(f,Ch);
 End;
 Close(f);
 Close(f0);
 Erase(f0);
 Rename(f,F0Name);
End.