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#pragma GCC optimize ("O3")
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;
const int INF = 0x3f3f3f3f;

#define FOR(i,b,e) for(int i = (b); i < (e); i++)
#define TRAV(x,a) for(auto &x: (a))
#define SZ(x) ((int)x.size())
#define PB push_back
#define X first
#define Y second

const int mod = 1e9+7;
const int N = 5e5+5;

struct vertex{
	int leftInt, rightInt;
	int parent, leftSon, rightSon;
	bool increasing;
};

int n, ans;
vertex v[N];
int lewy[N], prawy[N];
vi indexy;

bool inRange(int a, int b, int c){
	return b <= a && a <= c;
}

void zmienSyna(int p, int oldRoot, int newRoot){
	if(p == -1) return;
	if(v[p].leftSon == oldRoot){
		v[p].leftSon = newRoot;
		return;
	}
	if(v[p].rightSon == oldRoot){
		v[p].rightSon = newRoot;
		return;
	}
}

int rotuj(int root, bool syn, int cel){
	int wRoocie = (v[root].increasing ? v[root].leftInt : v[root].rightInt);
	ans = (ans + abs(cel-wRoocie)) % mod;
	if(syn == 0){
		int newRoot = v[root].leftSon;
		v[root].leftSon = -1;
		v[root].leftInt = cel+1;
		v[newRoot].rightInt = cel;
		v[root].increasing = 1;
		zmienSyna(v[root].parent, root, newRoot);
		v[newRoot].rightSon = root;
		v[newRoot].parent = v[root].parent;
		v[root].parent = newRoot;
		if(v[newRoot].leftInt != cel){
			int newSon = indexy.back();
			indexy.pop_back();
			v[newSon] = v[newRoot];
			v[newSon].rightInt = cel-1;
			v[newSon].parent = newRoot;
			v[newSon].rightSon = -1;
			v[newRoot].leftInt = cel;
			if(v[newRoot].leftSon != -1) v[v[newRoot].leftSon].parent = newSon;
			v[newRoot].leftSon = newSon;
		}
		return newRoot;
	}
	else{
		int newRoot = v[root].rightSon;
		v[root].rightSon = -1;
		v[root].rightInt = cel-1;
		v[newRoot].leftInt = cel;
		v[root].increasing = 0;
		zmienSyna(v[root].parent, root, newRoot);
		v[newRoot].leftSon = root;
		v[newRoot].parent = v[root].parent;
		v[root].parent = newRoot;
		if(v[newRoot].rightInt != cel){
			int newSon = indexy.back();
			indexy.pop_back();
			v[newSon] = v[newRoot];
			v[newSon].leftInt = cel+1;
			v[newSon].parent = newRoot;
			v[newSon].leftSon = -1;
			v[newRoot].rightInt = cel;
			if(v[newRoot].rightSon != -1) v[v[newRoot].rightSon].parent = newSon;
			v[newRoot].rightSon = newSon;
		}
		return newRoot;
	}
}

void korzeniuj(int root, int cel, bool rozw);

void wyprostuj(int root, int cel, bool inc){
	if(!inc){
		int aktParent = v[root].parent;
		int aktValue = v[aktParent].leftInt-1;
		korzeniuj(root, aktValue, 0);
		root = v[aktParent].leftSon;
		int lSon = v[root].leftSon;
		if(lSon != -1 && !v[lSon].increasing && v[lSon].rightInt+1 == v[root].leftInt){
			indexy.PB(lSon);
			v[root].leftInt = v[lSon].leftInt;
			if(v[lSon].leftSon != -1) v[v[lSon].leftSon].parent = root;
			v[root].leftSon = v[lSon].leftSon;
			v[root].increasing = 0;
		}
		if(v[root].leftInt > cel){
			wyprostuj(v[root].leftSon, cel, inc);
			lSon = v[root].leftSon;
			indexy.PB(lSon);
			v[root].leftInt = v[lSon].leftInt;
			if(v[lSon].leftSon != -1) v[v[lSon].leftSon].parent = root;
			v[root].leftSon = v[lSon].leftSon;
			v[root].increasing = 0;
		}
	}
	else{
		int aktParent = v[root].parent;
		int aktValue = v[aktParent].rightInt+1;
		korzeniuj(root, aktValue, 0);
		root = v[aktParent].rightSon;
		int rSon = v[root].rightSon;
		if(rSon != -1 && v[rSon].increasing && v[rSon].leftInt-1 == v[root].rightInt){
			indexy.PB(rSon);
			v[root].rightInt = v[rSon].rightInt;
			if(v[rSon].rightSon != -1) v[v[rSon].rightSon].parent = root;
			v[root].rightSon = v[rSon].rightSon;
			v[root].increasing = 1;
		}
		if(v[root].rightInt < cel){
			wyprostuj(v[root].rightSon, cel, inc);
			rSon = v[root].rightSon;
			indexy.PB(rSon);
			v[root].rightInt = v[rSon].rightInt;
			if(v[rSon].rightSon != -1) v[v[rSon].rightSon].parent = root;
			v[root].rightSon = v[rSon].rightSon;
			v[root].increasing = 1;
		}
	}
}

void korzeniuj(int root, int cel, bool rozw){
	if(!inRange(cel, v[root].leftInt, v[root].rightInt)){
		int bottom = (v[root].increasing ? v[root].rightInt : v[root].leftInt);
		if(cel < bottom){
			wyprostuj(v[root].leftSon, cel, 0);
			root = rotuj(root, 0, cel);
		}
		else{
			wyprostuj(v[root].rightSon, cel, 1);
			root = rotuj(root, 1, cel);
		}
	}
	else if(!((cel == v[root].leftInt && v[root].increasing) ||
		      (cel == v[root].rightInt && !v[root].increasing))){
		int fake = indexy.back();
		indexy.pop_back();
		v[fake] = v[root];
		if(!v[root].increasing){
			v[fake].leftSon = root;
			v[fake].rightSon = -1;
		}
		else{
			v[fake].rightSon = root;
			v[fake].leftSon = -1;
		}
		zmienSyna(v[root].parent, root, fake);
		v[root].parent = fake;
		root = rotuj(fake, v[root].increasing, cel);
	}
	if(v[root].leftInt != cel){
		int newSon = indexy.back();
		indexy.pop_back();
		v[newSon] = v[root];
		v[newSon].rightInt = cel-1;
		v[newSon].parent = root;
		v[root].leftInt = cel;
		if(v[root].leftSon != -1) v[v[root].leftSon].parent = newSon;
		v[root].leftSon = newSon;
	}
	if(v[root].rightInt != cel){
		int newSon = indexy.back();
		indexy.pop_back();
		v[newSon] = v[root];
		v[newSon].leftInt = cel+1;
		v[newSon].parent = root;
		v[root].rightInt = cel;
		if(v[root].rightSon != -1) v[v[root].rightSon].parent = newSon;
		v[root].rightSon = newSon;
	}
	if(rozw && lewy[cel]){
		korzeniuj(v[root].leftSon, lewy[cel], 1);
	}
	if(rozw && prawy[cel]){
		korzeniuj(v[root].rightSon, prawy[cel], 1);
	}
}

void readInt(int &x){
    x = 0;
    char c = getchar();
    bool negative = 0;
    while(c < 33) c = getchar();
    if(c == '-') negative = 1, c = getchar();
    while('0' <= c && c <= '9') x = 10*x + c - '0', c = getchar();
    if(negative) x *= -1;
}

void solve(){
	int root1 = 0, root2 = 0;
	readInt(n);
	FOR(i, 1, n+1) v[i].leftSon = v[i].rightSon = -1;
	FOR(i, 1, n+1){
		int a;
		readInt(a);
		v[i].leftInt = v[i].rightInt = i;
		v[i].parent = a;
		v[i].increasing = 0;
		if(a == -1) root1 = i;
		else if(a < i) v[a].rightSon = i;
		else v[a].leftSon = i;
	}
	FOR(i, 1, n+1){
		int a;
		readInt(a);
		if(a == -1) root2 = i;
		else if(a < i) prawy[a] = i;
		else lewy[a] = i;
	}
	korzeniuj(root1, root2, 1);
	cout << ans << '\n';
}

int main(){
    // ios::sync_with_stdio(0);
    // cin.tie(0);
    // int tt; cin >> tt;
    // FOR(te, 0, tt)
    solve();
    return 0;
}