#yuki895

def combi(n,r,m):
 return fact[n]*pow(fact[r],m-2,m)*pow(fact[n-r],m-2,m)

mod=10**9+7
a,b,c=map(int,raw_input().split())
fact=[1]
for i in range(1,10**6):
 fact.append(i*fact[-1]%mod)

res=0
for i in range(b+c-1,a+b+c-1):
 res+=(pow(2,i,mod)-1)*combi(i-1,b-1,mod)*combi(i-b,c-1,mod)
 res%=mod
print res