program factorial;
var f,g:text;
    n,cn,c,p:longint;
begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
rewrite(g);
read(f,p);
n:=0;
c:=0;
while true do
  begin
    n:=n+5;
    cn:=n;
    c:=c+1;
    if (cn mod 25=0)then
    begin
    c:=c-1;
    while (cn mod 5=0)do
      begin
        cn:=cn div 5;
        c:=c+1;
      end;
    end;
    if (c=p)then break;
  end;
write(g,n);
close(f);
close(g);
end.