Python Key Generator with String dont work

import random


mod1 = "BOT"
mod2 = (random.randrange(1,9999))
mod3 = (random.randrange(1,9999))
mod4 = (random.randrange(1,9999))


key = mod1 + "-" + mod2 + "-" + mod3 + "-" + mod4
print(key)

When i run this i become the error: TypeError: can only concatenate str (not "int") to str

Can anyone Help me