def inv(x):
    return pow(x, MOD-2, MOD)

def C(n, r):
    return fact[n] * inv(fact[r]) * inv(fact[n-r])

a, b, c = map(int, input().split())
MOD = 10**9 + 7
fact = [1]

for i in range(1, 10**6):
    fact.append(i * fact[-1] % MOD)
    
ans = 0

for i in range(b+c-1, a+b+c-1): #iはyの最上位ビットの位置(0_indexed)
    ans += (2**i-1) * C(i-1, b-1) * C(i-b, c-1)
    ans %= MOD

print(ans)