program Fact;
var
   fl : text;
   k : longint;
   n, i, j, p : longint;

function citzero(l:longint):longint;
var
  aux, z, i : longint;
begin
   z := 0;
   for i := 1 to l do
         begin
          aux := i;
          while aux mod 5 = 0 do
             begin
               z := z + 1;
               aux := aux div 5;
           end;
        end;
   citzero := z;
end;

procedure cautabin(in1,in2:longint);
var
   m : longint;
begin
   m := (in1+in2) div 2;
   writeln(citzero(m));
   if p = citzero(m) then
      begin
         i := p;
         exit;
      end
   else
      if in1 < in2 then
          if p < citzero(m) then
             cautabin(in1,m-1)
          else
             cautabin(m+1,in2);

end;
begin
   assign(fl,'fact.in');
   reset(fl);
   readln(fl,p);
   close(fl);

   cautabin(1,1000000);

   assign(fl,'fact.out');
   rewrite(fl);
   writeln(fl,i);
   close(fl);
end.