#include <bits/stdc++.h>
#define int long long
#define boost ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
const int mod = 1e9 + 7;

vector<int> h, w, pref;
int ans = 0;

int bpow(int a, int n) {
	int res = 1;
	while(n > 0) {
		if(n & 1) {
			res *= a;
			res %= mod;
		}
		a *= a;
		a %= mod;
		n /= 2;
	}
	return res;
}

int C(int n, int k = 2) {
	int res = 1;
	for(int i = 1; i <= k; i++) {
		res = ((res * ((n - k + i) % mod)) % mod) * bpow(i, mod - 2);
	}
	return res;
}


//sub4
void solvesame() {
	int y = h[0];
	int x = 0;
	for(auto it: w) {
		x = (x + it) % mod;
	}
	cout << ((C(x + 1, 2) % mod) * (C(y + 1, 2) % mod)) % mod << endl;
}

//sub3
void solvesub3() {
	int n = h.size();
	int x = 0;
	for(auto it: w) {
		x = (x + it) % mod;
	}
	int ans = ((C(x + 1, 2) % mod));
	int prev = 0;
	for(int i = 0; i < n; i++) {
		if(h[i] == 1) {
			ans = (ans + ((C(prev + 1, 2) % mod) * (C(3, 2) % mod)) % mod) % mod;
			ans = (ans - (C(prev + 1, 2) % mod) + mod) % mod;
			prev = 0;
		} else {
			prev += w[i];
		}
	}
	ans = (ans + ((C(prev + 1, 2) % mod) * (C(3, 2) % mod)) % mod) % mod;
	ans = (ans - (C(prev + 1, 2) % mod) + mod) % mod;
	cout << ans << endl;
}

void solvesub5() {
	int n = h.size();
	int x = 0;
	for(auto it: w) {
		x = (x + it) % mod;
	}
	int ans = ((C(x + 1, 2) % mod) * (C(h[0] + 1, 2) % mod)) % mod;
	x = (x - w[0] + mod) % mod;
	for(int i = 1; i < n; i++) {
		ans = (ans + ((C(x + 1, 2) % mod) * (C(h[i] + 1, 2) % mod)) % mod) % mod;
		ans = (ans - ((C(x + 1, 2) % mod) * (C(h[i - 1] + 1, 2) % mod)) % mod + mod) % mod;
		x = (x - w[i] + mod) % mod;
	}
	cout << ans << endl;
}

void solvesub2() {
	int mxh = *max_element(h.begin(), h.end());
	int ans = 0;
	int n = h.size();

	for(int hi = 1; hi <= mxh; hi++) {
		int prev = 0;
		for(int i = 0; i < n; i++) {
			if(h[i] >= hi) {
				prev = (prev + w[i]) % mod;
			} else {
				ans = (ans + ((C(prev + 1, 2) % mod) * (C(hi + 1, 2) % mod)) % mod) % mod;
				ans = (ans - ((C(prev + 1, 2) % mod) * (C(hi, 2) % mod)) % mod + mod) % mod;
				prev = 0;
			}
		}
		ans = (ans + ((C(prev + 1, 2) % mod) * (C(hi + 1, 2) % mod)) % mod) % mod;
		ans = (ans - ((C(prev + 1, 2) % mod) * (C(hi, 2) % mod)) % mod + mod) % mod;
	}
	cout << ans << endl;
}

void solvesub6() {
	int ans = 0;
	int n = h.size();
	vector<int> his = h;
	sort(his.begin(), his.end());
	for(int hi = 0; hi < n; hi++) {
		int prev = 0;
		for(int i = 0; i < n; i++) {
			if(h[i] >= his[hi]) {
				prev = (prev + w[i]) % mod;
			} else {
				ans = (ans + ((C(prev + 1, 2) % mod) * (C(his[hi] + 1, 2) % mod)) % mod) % mod;
				if(hi > 0) ans = (ans - ((C(prev + 1, 2) % mod) * (C(his[hi - 1] + 1, 2) % mod)) % mod + mod) % mod;
				prev = 0;
			}
		}
		ans = (ans + ((C(prev + 1, 2) % mod) * (C(his[hi] + 1, 2) % mod)) % mod) % mod;
		if(hi > 0) ans = (ans - ((C(prev + 1, 2) % mod) * (C(his[hi - 1] + 1, 2) % mod)) % mod + mod) % mod;
	}
	cout << ans << endl;
}
main() {
	boost;
	int n;
	cin >> n;
	h.resize(n), w.resize(n), pref.resize(n + 1);
	for(int i = 0; i < n; i++) {
		cin >> h[i];
	}
	for(int i = 0; i < n; i++) {
		cin >> w[i];
		pref[i + 1] = pref[i] + w[i];
	}

	//subtasks
	bool sub4 = 1;
	bool sub3 = (h[0] <= 2);
	bool sub5 = 1;
	bool sub2 = (n <= 50 && h[0] <= 50);
	bool sub6 = (n <= 1000);
	//end subtasks

	//check subtask
	for(int i = 1; i < n; i++) {
		sub4 &= (h[i] == h[i - 1]);
		sub3 &= (h[i] <= 2);
		sub5 &= (h[i - 1] <= h[i]);
		sub2 &= (h[i] <= 50);
	}

	if(sub2) {
		solvesub2();
		return 0;
	}
	if(sub3) {
		solvesub3();
		return 0;
	}
	if(sub4) {
		solvesame();
		return 0;
	}
	if(sub5) {
		solvesub5();
		return 0;
	}
	if(sub6) {
		solvesub6();
		return 0;
	}
}