VirtualBox: two network interfaces (NAT and host-only ones) in a Debian guest on Ubuntu

I created a Debian VM on VirtualBox with two interfaces: a NAT one (for accessing internet) and a host-only one. However, I do not know how to make both interfaces work at the same time. If I the define the host-only as the adapter 1, I can access my VM from the host but not the internet; if I define the NAT one as adapter 1, I can access the internet but cannot reach my guest Debian.