#include #include using lint = long long; template struct ModInt { using lint = long long; int val; // constructor ModInt(lint v = 0) : val(v % MOD) { if (val < 0) val += MOD; }; // unary operator ModInt operator+() const { return ModInt(val); } ModInt operator-() const { return ModInt(MOD - val); } ModInt inv() const { return this->pow(MOD - 2); } // arithmetic ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; } ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; } ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; } ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; } ModInt pow(lint n) const { auto x = ModInt(1); auto b = *this; while (n > 0) { if (n & 1) x *= b; n >>= 1; b *= b; } return x; } // compound assignment ModInt& operator+=(const ModInt& x) { if ((val += x.val) >= MOD) val -= MOD; return *this; } ModInt& operator-=(const ModInt& x) { if ((val -= x.val) < 0) val += MOD; return *this; } ModInt& operator*=(const ModInt& x) { val = lint(val) * x.val % MOD; return *this; } ModInt& operator/=(const ModInt& x) { return *this *= x.inv(); } // compare bool operator==(const ModInt& b) const { return val == b.val; } bool operator!=(const ModInt& b) const { return val != b.val; } // I/O friend std::istream& operator>>(std::istream& is, ModInt& x) noexcept { return is >> x.val; } friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept { return os << x.val; } }; constexpr int MOD = 1e9 + 7; using mint = ModInt; void solve() { int n; mint p; std::cin >> n >> p; if (n == 1) { std::cout << 0 << std::endl; return; } std::vector xs(n); xs[0] = 0, xs[1] = 1; for (int i = 2; i < n; ++i) { xs[i] = xs[i - 1] * p + xs[i - 2]; } mint sum = 0, ans = 0; for (auto x : xs) { sum += x; ans += x * sum; } std::cout << ans << std::endl; } int main() { std::cin.tie(nullptr); std::cout.tie(nullptr); std::ios::sync_with_stdio(false); solve(); return 0; }