mo=10^9+7
main=do
 [n,a,b]<-map read.words<$>getLine
 print$flip mod mo$(p 2 n)-1-(f a)-(f b)
p a n
 |n==0=1
 |odd n=a*(p a(n-1))`mod`mo
 |even n=p(a*a`mod`mo)(div n 2)
f a b=(foldl(\s t->s*(a-t+1)`mod`mo)1[1..b])*(flip p(mo-2)$foldl1(\s t->s*t`mod`mo)[1..b])`mod`mo