Thunderwave. What Is That?

A creature in a 15 foot cube, originating from you must make a constitution saving throw. On a failed save, the creature takes two d eight thunder damage and is pushed ten feet away. On a successful save, it takes half as much damage and isn't pushed. So what am i rolling to prevent this? A constitution. Cause i didn't come up with leech constitution because, frankly, juston i just didn't think it was going to come up. And i'm just trying to be your spell casting yr. Your so it was 13 before, now it's 14, cause you got the plus one correct umber. Staff, o, the first one gets aan 11