var p,n2,n5,x,xx,nrzero:longint;
    f:text;
begin
assign(f,'fact.in');
reset(f);
readln(f,p);
Close(f);
if p=0
 then
  begin
  assign(f,'fact.out');
  rewrite(f);
  writeln(f,1);
  close(f);
  end
 else
  begin
   n2:=0;
   n5:=0;
   x:=1;
   nrzero:=0;
   while nrzero<>p do
    begin
      xx:=x;
      while xx mod 2=0 do
       begin
        inc(n2);
        xx:=xx div 2;
       end;
      while xx mod 5=0 do
       begin
        inc(n5);
        xx:=xx div 5;
       end;
       if n2<n5
        then
          nrzero:=n2
        else
          nrzero:=n5;
      inc(x);
     end;
     assign(f,'fact.out');
     rewrite(f);
     write(f,x-1);
     close(f);
  end;
end.