#define _USE_MATH_DEFINES #include using namespace std; template class Modular { private: long long value; public: constexpr Modular() : value() {}; constexpr Modular(const Modular& other) : value(other.value) {} template constexpr Modular(const U& x) { value = normalize(x); } template static long long normalize(const U& x) { long long v; if (-MOD <= x && x < MOD) v = static_cast(x); else v = static_cast(x % MOD); if (v < 0) v += MOD; return v; } constexpr long long inverse(long long x) { x = (x % MOD + MOD) % MOD; long long y = MOD, u = 1, v = 0; while(y) { long long t = x / y; x -= t * y; swap(x, y); u -= t * v; swap(u, v); } return (u % MOD + MOD) % MOD; } explicit operator long long() const noexcept { return value;} template explicit operator U() const noexcept { return static_cast(value); } constexpr Modular& operator=(const Modular& other) & noexcept { value = other.value; return *this; } template constexpr Modular& operator=(const U& other) & noexcept { return *this = Modular(other); } constexpr Modular& operator+=(const Modular& other) noexcept { if ((value += other.value) >= MOD) value -= MOD; return *this; } template constexpr Modular& operator+=(const U& other) noexcept { return *this += Modular(other); } constexpr Modular& operator-=(const Modular& other) noexcept { if ((value -= other.value) < 0) value += MOD; return *this; } template constexpr Modular& operator-=(const U& other) noexcept { return *this -= Modular(other); } constexpr Modular& operator*=(const Modular& other) noexcept { value = value * other.value % MOD; return *this; } template constexpr Modular& operator*=(const U& other) noexcept {return *this *= Modular(other); } constexpr Modular& operator/=(const Modular& other) noexcept { return *this *= Modular(inverse(other.value)); } template constexpr Modular& operator/=(const U& other) noexcept { return *this *= Modular(inverse(normalize(other))); } constexpr Modular& operator++() noexcept {return *this += 1; } constexpr Modular operator++(int) noexcept { Modular ret(*this); *this += 1; return ret; } constexpr Modular& operator--() noexcept {return *this -= 1; } constexpr Modular operator--(int) noexcept { Modular ret(*this); *this += 1; return ret; } constexpr Modular operator-() const { return Modular(-value); } friend constexpr bool operator==(const Modular& lhs, const Modular& rhs) noexcept { return lhs.value == rhs.value; } template friend constexpr bool operator==(const Modular& lhs, U rhs) noexcept { return lhs == Modular(rhs); } template friend constexpr bool operator==(U lhs, const Modular& rhs) noexcept { return Modular(lhs) == rhs; } friend constexpr bool operator!=(const Modular& lhs, const Modular& rhs) noexcept { return !(lhs == rhs); } template friend constexpr bool operator!=(const Modular& lhs, U rhs) noexcept { return !(lhs == rhs); } template friend constexpr bool operator!=(U lhs, const Modular rhs) noexcept { return !(lhs == rhs); } friend constexpr bool operator<(const Modular& lhs, const Modular& rhs) noexcept { return lhs.value < rhs.value; } template friend constexpr bool operator<(const Modular &lhs, U rhs) noexcept { return lhs.value < rhs; } template friend constexpr bool operator<(U lhs, const Modular &rhs) noexcept { return lhs < rhs.value; } friend constexpr bool operator>(const Modular& lhs, const Modular& rhs) noexcept { return rhs.value < lhs.value; } template friend constexpr bool operator>(const Modular &lhs, U rhs) noexcept { return rhs.value < lhs; } template friend constexpr bool operator>(U lhs, const Modular &rhs) noexcept { return rhs < lhs.value; } friend constexpr bool operator<=(const Modular& lhs, const Modular& rhs) noexcept { return !(lhs.value > rhs.value); } template friend constexpr bool operator<=(const Modular &lhs, U rhs) noexcept { return !(lhs.value > rhs); } template friend constexpr bool operator<=(U lhs, const Modular &rhs) noexcept { return !(lhs < rhs.value); } friend constexpr bool operator>=(const Modular& lhs, const Modular& rhs) noexcept { return !(lhs.value < rhs.value); } template friend constexpr bool operator>=(const Modular &lhs, U rhs) noexcept { return !(lhs.value < rhs); } template friend constexpr bool operator>=(U lhs, const Modular &rhs) noexcept { return !(lhs < rhs.value); } friend constexpr Modular operator+(const Modular& lhs, const Modular& rhs) noexcept { return Modular(lhs) += rhs; } template friend constexpr Modular operator+(const Modular& lhs, U rhs) noexcept { return Modular(lhs) += rhs; } template friend constexpr Modular operator+(U lhs, const Modular &rhs) noexcept { return Modular(lhs) += rhs; } friend constexpr Modular operator-(const Modular& lhs, const Modular& rhs) noexcept { return Modular(lhs) -= rhs; } template friend constexpr Modular operator-(const Modular& lhs, U rhs) noexcept { return Modular(lhs) -= rhs; } template friend constexpr Modular operator-(U lhs, const Modular &rhs) noexcept { return Modular(lhs) -= rhs; } friend constexpr Modular operator*(const Modular& lhs, const Modular& rhs) noexcept { return Modular(lhs) *= rhs; } template friend constexpr Modular operator*(const Modular& lhs, U rhs) noexcept { return Modular(lhs) *= rhs; } template friend constexpr Modular operator*(U lhs, const Modular &rhs) noexcept { return Modular(lhs) *= rhs; } friend constexpr Modular operator/(const Modular& lhs, const Modular& rhs) noexcept { return Modular(lhs) /= rhs; } template friend constexpr Modular operator/(const Modular& lhs, U rhs) noexcept { return Modular(lhs) /= rhs; } template friend constexpr Modular operator/(U lhs, const Modular &rhs) noexcept { return Modular(lhs) /= rhs; } friend std::ostream& operator<<(std::ostream& stream, const Modular& number) noexcept { return stream << number.value; } friend std::istream& operator>>(std::istream& stream, Modular& number) { long long in; stream >> in; number.value = Modular::normalize(in); return stream; } constexpr int getmod() const { return MOD; } }; template Modular power(const Modular& x, const U& y) { assert(y >= 0); Modular k = x, result = 1; U p = y; while (p > 0) { if (p & 1) result *= k; k *= k; p >>= 1; } return result; } template class BinaryCoefficients { private: vector> fact_, inv_, finv_; public: constexpr BinaryCoefficients(int n = 2020200) : fact_(n, 1), inv_(n, 1), finv_(n, 1) { for (int i = 2; i < n; i++) { fact_[i] = fact_[i - 1] * i; inv_[i] = -inv_[MOD % i] * (MOD / i); finv_[i] = finv_[i - 1] * inv_[i]; } } constexpr Modular comb(int n, int k) const noexcept { if (n < k || n < 0 || k < 0) return 0; return fact_[n] * finv_[k] * finv_[n - k]; } constexpr Modular fact(int n) const noexcept { if (n < 0) return 0; return fact_[n]; } constexpr Modular inv(int n) const noexcept { if (n < 0) return 0; return inv_[n]; } constexpr Modular finv(int n) const noexcept { if (n < 0) return 0; return finv_[n]; } }; constexpr int mod = 1e9 + 7; //constexpr int mod = 998244353; using mint = Modular; using bicoef = BinaryCoefficients; mint pow2[303030]; signed main() { ios::sync_with_stdio(false); cin.tie(0); bicoef bc; pow2[0] = 1; for (int i = 1; i < 303030; i++) { pow2[i] = pow2[i - 1] * 2; } int a, b, c; cin >> a >> b >> c; mint ans = 0; for (int i = 1; i + 1 < a + b + c; i++) { ans += (pow2[i] - 1) * bc.comb(i - 1, c - 1) * bc.comb(i - c, b - 1); } cout << ans << '\n'; return 0; }