program fact;
var
 p,numar,i,temp:longint;
 fin,fout:text;
 gasit:boolean;
begin
 assign(fin,'fact.in');
 reset(fin);
 read(fin,p);
 close(fin);
 i:=1;
 while (numar<p) do
  begin
   i:=i+1;
   temp:=i;
   while temp mod 5=0 do
    begin
     numar:=numar+1;
     temp:=temp div 5;
    end;
  end;
 assign(fout,'fact.out');
 rewrite(fout);
 write(fout,i);
 close(fout);
end.