/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author majk
 */

#ifndef MAJK_LIB
#define MAJK_LIB

#include <vector>
#include <stack>
#include <iostream>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <iomanip>
#include <set>
#include <functional>
#include <fstream>
#include <algorithm>
#include <cassert>
#include <cmath>
#include <string>
#include <sstream>
#include <queue>
#include <bitset>
using namespace std;

#define x first
#define y second
typedef std::pair<int,int> pii; typedef long long ll; typedef unsigned long long ull; typedef unsigned int ui; typedef pair<ui,ui> puu;

template <typename T, typename U> std::istream&operator>>(std::istream&i, pair<T,U>&p) {i >> p.x >> p.y; return i;}
template<typename T>std::istream&operator>>(std::istream&i,vector<T>&t) {for(auto&v:t){i>>v;}return i;}
template <typename T, typename U> std::ostream&operator<<(std::ostream&o, const pair<T,U>&p) {o << p.x << ' ' << p.y; return o;}
template<typename T>std::ostream&operator<<(std::ostream&o,const vector<T>&t) {if(t.empty())o<<'\n';for(size_t i=0;i<t.size();++i){o<<t[i]<<" \n"[i == t.size()-1];}return o;}
template<typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
template <typename T> bool in(T a, T b, T c) { return a <= b && b < c; }
ui logceil(int x) { return 8*sizeof(int)-__builtin_clz(x); }

namespace std { template<typename T,typename U>struct hash<pair<T,U>>{hash<T>t;hash<U>u;size_t operator()(const pair<T,U>&p)const{return t(p.x)^(u(p.y)<<7);}}; }
template<typename T,typename F>T bsh(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){l=m+1;r=m;}else{h=m-1;}}return r;}
template<typename F> double bshd(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){l=m;}else{h=m;}}return (l+h)/2;}
template<typename T,typename F>T bsl(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){h=m-1;r=m;}else{l=m+1;}}return r;}
template<typename F> double bsld(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){h=m;}else{l=m;}}return (l+h)/2;}
template<typename T> T gcd(T a,T b) { if (a<b) swap(a,b); return b?gcd(b,a%b):a; }

template<typename T>class vector2:public vector<vector<T>>{public:vector2(){} vector2(size_t a,size_t b,T t=T()):vector<vector<T>>(a,vector<T>(b,t)){}};
template<typename T>class vector3:public vector<vector2<T>>{public:vector3(){} vector3(size_t a,size_t b,size_t c,T t=T()):vector<vector2<T>>(a,vector2<T>(b,c,t)){}};
template<typename T>class vector4:public vector<vector3<T>>{public:vector4(){} vector4(size_t a,size_t b,size_t c,size_t d,T t=T()):vector<vector3<T>>(a,vector3<T>(b,c,d,t)){}};
template<typename T>class vector5:public vector<vector4<T>>{public:vector5(){} vector5(size_t a,size_t b,size_t c,size_t d,size_t e,T t=T()):vector<vector4<T>>(a,vector4<T>(b,c,d,e,t)){}};


#endif

class Fraction {
    friend ostream& operator<<(ostream& os, const Fraction& f);
public:
    Fraction(ll u, ll v = 1) : u(u), v(v) { norm(); }
    bool operator==(const Fraction & o) const { return u == o.u && v == o.v; }
    bool operator!=(const Fraction & o) const { return u != o.u || v != o.v; }
    bool operator<(const Fraction &o) const { return u*o.v < o.u*v; }
    bool operator<=(const Fraction &o) const { return u*o.v <= o.u*v; }
    bool operator>(const Fraction &o) const { return u*o.v > o.u*v; }
    bool operator>=(const Fraction &o) const { return u*o.v >= o.u*v; }
    Fraction operator-(const Fraction& o) { return Fraction(-u, v); }
    Fraction& operator+=(const Fraction& o) { u = u * o.v + v * o.u; v *= o.v; return norm(); }
    Fraction& operator-=(const Fraction& o) { u = u * o.v - v * o.u; v *= o.v; return norm(); }
    Fraction& operator/=(const Fraction& o) { u = u * o.v; v = o.u * v; return norm(); }
    Fraction& operator*=(const Fraction& o) { u *= o.u; v *= o.v; return norm(); }
    Fraction operator+(const Fraction& o) const { Fraction f(*this); return f += o; }
    Fraction operator-(const Fraction& o) const { Fraction f(*this); return f -= o; }
    Fraction operator*(const Fraction& o) const { Fraction f(*this); return f *= o; }
    Fraction operator/(const Fraction& o) const { Fraction f(*this); return f /= o; }

private:
    Fraction& norm() {
        ll g = gcd(abs(u),abs(v));
        u /= g;
        v /= g;
        if (v < 0) { u = -u; v = -v; }
        return *this;
    }

    ll u,v;
};


ostream& operator<<(ostream& os, const Fraction& f) {
    os << f.u << '/' << f.v;
    return os;
}
struct compare {
    bool operator()(const pii &a, const pii &b) const {
        return ll(a.x)*b.y < ll(b.x)*a.y;
    }
};

bool leq(const pii &a, const pii &b) {
    return ll(a.x)*b.y <= ll(b.x)*a.y;
}

pii plus(const pii&a, const pii&b) {
    return {a.x+b.x,a.y+b.y};
}

typedef multiset<pii, compare> MS;


class F {
public:
    vector<vector<int>> E;
    vector<int> B;
    ll ans;

    MS *merge(MS *A, MS *B) {
        if (A->size() < B->size()) return merge(B,A);
        else {
            for (auto each = B->begin(); each != B->end(); ++each ) {
                A->insert(*each);
            }
            return A;
        }
    }

    MS* run(int v) {
        pii f{ B[v], 1 - B[v]};
        MS *r = new MS;
        for (int u:E[v]) {
            auto z = run(u);
            r = merge(r, z);
        }

        while (!r->empty() && leq(*(r->begin()), f)) {
            ans += f.x * ll(r->begin()->y/* - r->begin()->x*/);
            f.x += r->begin()->x;
            f.y += r->begin()->y;
            r->erase(r->begin());
        }
        r->insert(f);
        return r;
    }

    void solve(istream& cin, ostream& cout) {
        int N; cin >> N;
        if (N == 1) {
            cout << "0\n";
            return;
        }

        ans = 0;

        vector<int> P(N-1);
        B.resize(N);

        cin >> P >> B;

        E.resize(N);
        for (int i = 0; i < N-1; ++i) {
            E[P[i]-1].push_back(i+1);
        }

        auto r = run(0);
        vector<int> Z, O;
        for (auto each = r->begin(); each != r->end(); ++each ) {
            Z.push_back(each->y/* - each->x*/);
            O.push_back(each->x);
        }
        Z.push_back(0LL);
        for (int i = O.size()-1; i >= 0; --i) Z[i] += Z[i+1];
        for (int i = O.size()-1; i >= 0; --i) ans += ll(O[i]) * Z[i+1];

        cout << ans << endl;
    }
};


int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	F solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
    return 0;
}


Measured memory_bytes: 43948