def aa(q,w):
    if w<0 or q<w:
        return 0
    global mod
    return f[q]*g[w]%mod*g[q-w]%mod

mod=10**9+7
f=[1]*(10**6+1);g=[1]*len(f)
for i in range(1,len(f)):
    f[i]=f[i-1]*i%mod
g[-1]=pow(f[-1],mod-2,mod)
for i in range(10**6,0,-1):
    g[i-1]=g[i]*i%mod
a,b,c=map(int,input().split());ans=0;b-=1
for i in range(1,a+1):
	e=aa(a-i+b,b)*aa(a-i+b+c-1,c-1)%mod
	ans+=e*(pow(2,a-i+b+c,mod)-1)%mod
print(ans%mod)