//
// Created by liasa on 11/11/2025.
//
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vll vector<ll>
const ll mod = 1e9 + 7;
ll pw(ll a, ll b) {
ll ans = 1;
while (b) {
if (b & 1) {
ans = (ans * a) % mod;
b--;
}
b /= 2;
a = (a * a) % mod;
}
return ans;
}
ll invi(ll x) { return pw(x, mod - 2); }
ll mul(ll a, ll b) { return (ll)((__int128)a * b % mod); }
ll addi(ll H, ll W) {
H++;
W++;
ll a = mul(H % mod, (H - 1) % mod);
ll b = mul(W % mod, (W - 1) % mod);
ll inv2 = invi(2);
ll ans = mul(mul(a, b), mul(inv2, inv2));
return ans;
}
ll CH(ll H) {
H++;
ll inv2 = invi(2);
return mul(mul(H % mod, (H - 1) % mod), inv2);
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n;
cin >> n;
vll h(n), w(n);
for (ll i = 0; i < n; i++)
cin >> h[i];
vll pre(n + 1, 0);
for (ll i = 0; i < n; i++) {
cin >> w[i];
pre[i + 1] = pre[i] + w[i];
}
ll ans = 0;
for (ll i = 0; i < n; i++) {
ans += addi(h[i], w[i]);
ans = (ans + mod) % mod;
}
vector<ll> s;
for (ll i = 0; i <= n; i++) {
ll cur = (i < n ? h[i] : -1);
while (!s.empty() && h[s.back()] >= cur) {
ll j = s.back();
s.pop_back();
ll L = s.empty() ? 0 : s.back() + 1, R = i - 1;
ll sum_l = pre[j + 1] - pre[L];
ll sum_r = pre[R + 1] - pre[j];
ll fixi = CH(h[j]);
ll ad = mul(
((mul(sum_l % mod, sum_r % mod) - mul(w[j] % mod, w[j] % mod) + mod) %
mod),
fixi);
ans += ad;
ans = (ans + mod) % mod;
}
if (i < n)
s.push_back(i);
}
cout << ans;
}
