var n:longint;
    p:longint;
    f:text;

procedure citire;
var f:text;
begin
     assign(f,'fact.in');
     reset(f);
     read(f,p);
     close(f);
end;

function cinci(n:longint):longint;
begin
     if n mod 5 = 0 then cinci:=1+cinci(n div 5)
     else cinci:=0;
end;

begin
     citire;
     assign(f,'fact.out');
     rewrite(f);
     n:=0;
     if p=0 then write (f,'1')
     else begin while p>0 do
                      begin
                           n:=n+5;
                           p:=p-cinci(n);
                      end;
                write(f,n);
          end;
     close(f);
end.