"Sto lat, sto lat niech żyje żyje nam! Sto lat, sto lat niech żyje żyje nam! Jeszcze raz,jeszcze raz, niech żyje nam, Niech żyje nam!"
However, this is traditionally immediatelly followed by a little more complicated song: "Niech mu gwiazdka pomyslności nigdy nie zagaśnie, nigdy nie zagaśnie. A kto z nami nie wypije niech go piorun trzaśnie!" (with nomerous regional variations) making it a single combined song effectively.
Melody: in most circumstances the melody for "Sto lat" , though quite easy, is not really relevant if only a rythm is kept. It's always sung in groups, so there is either a person much louder that you who you can simply follow, or - if noone wants to sing it loud enough, then probably the occasion is not correct to sing it at all. The second part ("gwiazdka pomyślności") is considered hard enough for foreigners therefore not knowing it is not a shame at all. However, most Poles will usually very positively welcome any (successfull or unsuccessfull) attempts to sing it.