#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; template struct modint { private: unsigned int value; static constexpr int mod() {return m;} public: constexpr modint(const long long x = 0) noexcept { long long y = x; if(y < 0 || y >= mod()) { y %= mod(); if(y < 0) y += mod(); } value = (unsigned int)y; } constexpr unsigned int val() noexcept {return value;} constexpr modint &operator+=(const modint &other) noexcept { value += other.value; if(value >= mod()) value -= mod(); return *this; } constexpr modint &operator-=(const modint &other) noexcept { unsigned int x = value; if(x < other.value) x += mod(); x -= other.value; value = x; return *this; } constexpr modint &operator*=(const modint &other) noexcept { unsigned long long x = value; x *= other.value; value = (unsigned int) (x % mod()); return *this; } constexpr modint &operator/=(const modint &other) noexcept { return *this *= other.inverse(); } constexpr modint inverse() const noexcept { assert(value); long long a = value,b = mod(),x = 1,y = 0; while(b) { long long q = a/b; a -= q*b; swap(a,b); x -= q*y; swap(x,y); } return modint(x); } constexpr modint power(long long N) const noexcept { assert(N >= 0); modint p = *this,ret = 1; while(N) { if(N & 1) ret *= p; p *= p; N >>= 1; } return ret; } constexpr modint operator+() {return *this;} constexpr modint operator-() {return modint() - *this;} constexpr modint &operator++(int) noexcept {return *this += 1;} constexpr modint &operator--(int) noexcept {return *this -= 1;} friend modint operator+(const modint& lhs, const modint& rhs) {return modint(lhs) += rhs;} friend modint operator-(const modint& lhs, const modint& rhs) {return modint(lhs) -= rhs;} friend modint operator*(const modint& lhs, const modint& rhs) {return modint(lhs) *= rhs;} friend modint operator/(const modint& lhs, const modint& rhs) {return modint(lhs) /= rhs;} friend ostream &operator<<(ostream &os,const modint &x) {return os << x.value;} }; //using mint = modint<998244353>; using mint = modint<1000000007>; int N,P; mint A[1 << 21]; void solve() { cin >> N >> P; A[0] = 0,A[1] = 1; for(int i = 2;i < N;i++) A[i] = P*A[i-1]+A[i-2]; mint S = 0,ans = 0; for(int i = 0;i < N;i++) { S += A[i]; ans += S*A[i]; } cout << ans << endl; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int tt = 1; //cin >> tt; while(tt--) solve(); }