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// Karol Kosinski 2020
#include <cstdio>
#include <utility>
#include <queue>
#define FR_(i,a,b) for(int i=(a);i<=(b);++i)
#define FD_(i,b,a) for(int i=(b);i>=(a);--i)
//#define DEBUG(x...) printf(x)
#define DEBUG(x...)
using namespace std;

//typedef long long LL;
const int NX = 500'003;
const int MOD = 1'000'000'007;

int ipre;
int Aim[NX], LA[NX], RA[NX];
int Par[NX], L[NX], R[NX], S[NX];
int LinL[NX], LinR[NX];

void fill_rec(int v)
{
    if (L[v] != 0) fill_rec(L[v]);
    if (R[v] != 0) fill_rec(R[v]);
    int left = L[v], right = R[v];
    int aux = (LinL[left] + LinR[right]) % MOD;
    S[v] = S[left] + 1 + S[right];
    LinL[v] = (aux + S[right]) % MOD;
    LinR[v] = (aux + S[left]) % MOD;
}

void print_tabs(int n)
{
    FR_(i,1,n) DEBUG("%4d", i);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", Par[i]);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", L[i]);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", R[i]);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", S[i]);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", LinL[i]);
    DEBUG("\n");
    FR_(i,1,n) DEBUG("%4d", LinR[i]);
    DEBUG("\n\n");
}

int count(int x, int aim_root, int& mlp, int& mrp)
{
    int res = 0;
    int l_lin = LinL[ L[x] ], r_lin = LinR[ R[x] ];
    int l_nodes = S[ L[x] ], r_nodes = S[ R[x] ];
    mlp = mrp = x;
    do {
        int px = Par[x];
        if (x == L[px])
        {
            res = (res + r_lin) % MOD;
            res = (res + 2 * r_nodes + 1) % MOD;
            DEBUG("[L %d]  res = %d\n", x, res);
            while (px != aim_root and px == L[ Par[px] ])
            {
                x = px;
                px = Par[px];
                res = (res + LinR[ R[x] ]) % MOD;
                res = (res + 2 * S[ R[x] ] + 1) % MOD;
                DEBUG("+[L %d] res = %d\n", x, res);
                r_nodes += S[ R[x] ] + 1;
            }
            r_lin = LinR[ R[px] ];
            r_nodes += S[ R[px] ] + 1;
            mrp = px;
        }
        else // x == R[px]
        {
            res = (res + l_lin) % MOD;
            res = (res + 2 * l_nodes + 1) % MOD;
            DEBUG("[R %d]  res = %d\n", x, res);
            while (px != aim_root and px == R[ Par[px] ])
            {
                x = px;
                px = Par[px];
                res = (res + LinL[ L[x] ]) % MOD;
                res = (res + 2 * S[ L[x] ] + 1) % MOD;
                DEBUG("+[R %d] res = %d\n", x, res);
                l_nodes += S[ L[x] ] + 1;
            }
            l_lin = LinL[ L[px] ];
            l_nodes += S[ L[px] ] + 1;
            mlp = px;
        }
        x = px;
    } while (x != aim_root);
    return res;
}

void update(int x, int old_x, int left, int right)
{
    int f = S[ L[left] ], g = S[ R[right] ];
    int fl = LinL[ L[left] ], gr = LinR[ R[right] ];
    
    if (old_x == L[ Par[old_x] ]) L[ Par[old_x] ] = x;
    else R[ Par[old_x] ] = x;
    
    Par[x] = Par[old_x];
    if (x != left) L[x] = x - 1;
    if (x != right) R[x] = x + 1;
    S[x] = f + g + right - left + 1;
    FR_(i, left, x - 1)
    {
        Par[i] = i + 1;
        if (i != left) L[i] = i - 1;
        R[i] = 0;
        LinL[i] = fl;
        LinR[i] = (fl + f) % MOD;
        S[i] = ++f;
    }
    FD_(i, right, x + 1)
    {
        Par[i] = i - 1;
        L[i] = 0;
        if (i != right) R[i] = i + 1;
        LinL[i] = (gr + g) % MOD;
        LinR[i] = gr;
        S[i] = ++g;
    }
    int aux = (LinL[ L[x] ] + LinR[ R[x] ]) % MOD;
    LinL[x] = (aux + S[ R[x] ]) % MOD;
    LinR[x] = (aux + S[ L[x] ]) % MOD;
}

int calc_result(int n, int root, int aim_root)
{
    int sum = 0;
    queue<pair<int, int>> Q;
    Q.emplace(aim_root, root);
    while (not Q.empty())
    {
        auto& p = Q.front();
        DEBUG("--[ %d  -->  %d ]--\n", p.first, p.second);
        if (p.first != p.second)
        {
            int mlp, mrp;
            sum += count(p.first, p.second, mlp, mrp);
            sum %= MOD;
            update(p.first, p.second, mlp, mrp);
            //print_tabs(n);              // DEBUG
        }
        if (LA[p.first] != 0) Q.emplace(LA[p.first], L[p.first]);
        if (RA[p.first] != 0) Q.emplace(RA[p.first], R[p.first]);
        Q.pop();
        DEBUG("sum = %d\n", sum);
    }
    return sum;
}

int main()
{
    int n, root, aim_root, sum = 0;
    scanf("%d", &n);
    FR_(i,1,n) scanf("%d", Par + i);
    FR_(i,1,n) scanf("%d", Aim + i);
    FR_(i,1,n)
    {
        if (Par[i] == -1) root = i; 
        else if (i < Par[i]) L[ Par[i] ] = i;
        else R[ Par[i] ] = i;
        if (Aim[i] == -1) aim_root = i;
        else if (i < Aim[i]) LA[ Aim[i] ] = i;
        else RA[ Aim[i] ] = i;
    }
    fill_rec(root);
    //print_tabs(n);             // DEBUG
    printf("%d\n", calc_result(n, root, aim_root));
    return 0;
}