var p,i,nr1,j:longint;
    nr:byte;
begin
assign(input,'fact.in');reset(input);read(p);
assign(output,'fact.out');rewrite(output);
if p=0 then write('1')
       else begin nr:=0;i:=0;
                     while nr1<p do begin
                         i:=i+5;
                         j:=i;
                         nr:=0;
                         while j mod 5=0 do begin
                                                inc(nr);
                                                j:=j div 5;

                                                end;
                         nr1:=nr1+nr;
                         end;
                write(i);
             end;
end.