var p2,p5,min:integer;
    i,k,p:longint;
    f,g:text;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
p2:=0;
p5:=0;
min:=0;
i:=1;
while min<p do
      begin
      inc(i);
      k:=i;
      while k mod 2=0 do
            begin
            inc(p2);
            k:=k div 2;
            end;
      while k mod 5=0 do
            begin
            inc(p5);
            k:=k div 5;
            end;
      if p2<p5 then min:=p2
               else min:=p5;
      end;
write(g,i);
close(f);
close(g);
end.