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

function citzero(l:longint):longint;
var
  aux, z : longint;
begin
   aux := l;
   z := 0;
   while aux mod 5 = 0 do
     begin
        z := z + 1;
        aux := aux div 5;
     end;
   citzero := z;
end;
begin
   assign(fl,'fact.in');
   reset(fl);
   readln(fl,p);
   close(fl);

   k := 0;
   i := 1;
   while k <> p do
      begin
         i := i + 1;
         k := k + citzero(i);
      end;

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