program fact;
var f : text;
    p, n, k, x, l : longint;
begin
assign (f, 'fact.in');
reset (f);
read (f, p);
close (f);
k:=0;
l:=0;
repeat
 inc (k);
 if (k mod 5=0) or (k mod 10=0) then inc (l);
 if (k mod 10<>0) and (k mod 5=0) then begin
                                        x:=k div 5;
                                        while x mod 5=0 do begin
                                                            inc (l);
                                                            x:=x div 5;
                                                           end;
                                       end;
until l=p;
assign (f, 'fact.out');
rewrite (f);
write (f, k);
close (f);
end.