var n,i,nr0,tmp: longint;
	f,g:text;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
	read(f,n);
	i := 5;
	while (i<=n) do
	begin
		nr0 := 0;
		tmp := i;
		while (tmp > 0) do
		begin
			nr0 := nr0 + tmp div 5;
			tmp := tmp div 5;
		end;
		if (nr0 = n)then 
			begin
				writeln(g,i);
                        	break;
                        end
		else 
			begin
				writeln(g,-1);	
				break;
			end;
	end;		
close(g);
end.