Case expression not constant

[Derrek]

hello, im making a simple rpg and this error kept coming up, and i dont know how to fix it. these are the cases i have.

switch (job)
{
case "human": hp << 100;
break;
case "troll": hp << 120;
break;
case "elf": hp << 90;
break;
case "wizard": hp << 80;
break;
}