#include using namespace std; using Int = long long; const char newl = '\n'; template inline void chmin(T1 &a,T2 b){if(a>b) a=b;} template inline void chmax(T1 &a,T2 b){if(a void drop(const T &x){cout< vector read(size_t n){ vector ts(n); for(size_t i=0;i>ts[i]; return ts; } template struct Mint{ static constexpr T mod = MOD; T v; Mint():v(0){} Mint(signed v):v(v){} Mint(long long t){v=t%MOD;if(v<0) v+=MOD;} Mint pow(long long k){ Mint res(1),tmp(v); while(k){ if(k&1) res*=tmp; tmp*=tmp; k>>=1; } return res; } static Mint add_identity(){return Mint(0);} static Mint mul_identity(){return Mint(1);} Mint inv(){return pow(MOD-2);} Mint& operator+=(Mint a){v+=a.v;if(v>=MOD)v-=MOD;return *this;} Mint& operator-=(Mint a){v+=MOD-a.v;if(v>=MOD)v-=MOD;return *this;} Mint& operator*=(Mint a){v=1LL*v*a.v%MOD;return *this;} Mint& operator/=(Mint a){return (*this)*=a.inv();} Mint operator+(Mint a) const{return Mint(v)+=a;} Mint operator-(Mint a) const{return Mint(v)-=a;} Mint operator*(Mint a) const{return Mint(v)*=a;} Mint operator/(Mint a) const{return Mint(v)/=a;} Mint operator-() const{return v?Mint(MOD-v):Mint(v);} bool operator==(const Mint a)const{return v==a.v;} bool operator!=(const Mint a)const{return v!=a.v;} bool operator <(const Mint a)const{return v constexpr T Mint::mod; template ostream& operator<<(ostream &os,Mint m){os< class Enumeration{ using M = M_; protected: static vector fact,finv,invs; public: static void init(Int n){ n=min(n,M::mod-1); Int m=fact.size(); if(n=m;i--) finv[i-1]=finv[i]*M(i); for(Int i=m;i<=n;i++) invs[i]=finv[i]*fact[i-1]; } static M Fact(Int n){ init(n); return fact[n]; } static M Finv(Int n){ init(n); return finv[n]; } static M Invs(Int n){ init(n); return invs[n]; } static M C(Int n,Int k){ if(n vector Enumeration::fact=vector(); template vector Enumeration::finv=vector(); template vector Enumeration::invs=vector(); //INSERT ABOVE HERE signed main(){ cin.tie(0); ios::sync_with_stdio(0); Int n,m; cin>>n>>m; vector as(n+1); for(Int i=2;i<=n;i++) cin>>as[i]; for(Int &a:as) a--; using M = Mint; using E = Enumeration; E::init(3e6); M ans{0}; vector toN(n+1,0); vector> G(n+1); vector po(n+1); for(Int i=2;i<=n;i++) po[i]=M(as[i]).pow(m-1); auto inv=[&](Int d){return d<0?-E::Invs(-d):E::Invs(d);}; auto calc=[&](Int i,Int j){ assert(i!=j); assert(1>q; for(Int i=0;i>x>>y; if(y==n){ enable(x); }else{ if(!toN[y]) G[y].emplace_back(x); else ans+=calc(x,y); } cout<