#include <bits/stdc++.h>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
ll exp(ll a, ll b) {
ll ans = 1;
while(b) {
if(b & 1) ans = (ans * a) % mod;
a = (a * a) % mod;
b /= 2;
}
return ans;
}
ll inv(ll a) {
return exp(a, mod - 2);
}
ll C(ll a) {
return a * (a + 1) % mod * inv(2) % mod;
}
ll S(ll l, ll r) {
return (C(r) - C(l-1) + mod) % mod;
}
int32_t main() {
ios_base::sync_with_stdio(false);
cout.tie(0); cin.tie(0);
int n;
cin >> n;
vector<ll> h(n+1), w(n+1);
for(int i=1; i<=n; i++) cin >> h[i];
for(int i=1; i<=n; i++) cin >> w[i];
set<ll> s;
for(int i=1; i<=n; i++) s.insert(h[i]);
if(s.size() == 1) {
ll W = 0, H = h[1];
for(int i=1; i<=n; i++) W = (W + w[i]) % mod;
cout << C(W) * C(H) % mod << '\n';
return 0;
}
bool inc = true;
for(int i=1; i<n; i++) if(h[i] > h[i+1]) inc = false;
if(inc) {
ll ans = 0, W = 0;
for(int i=n; i>=1; i--) {
W = (W + w[i]) % mod;
ans = (ans + S(W-w[i]+1, W) * C(h[i])) % mod;
}
cout << ans << '\n';
return 0;
}
if(n <= 1000) {
ll ans = 0;
vector<ll> pref(n+1);
for(int i=1; i<=n; i++) pref[i] = (pref[i-1] + w[i]) % mod;
auto query = [&](int l, int r) { return ( l > r ? 0 : (pref[r] - pref[l-1] + mod) % mod ); };
for(int i=1; i<=n; i++) {
ll H = h[i];
for(int j=i+1; j<=n; j++) {
H = min(H, h[j]);
//cout << H << " " << query(i, j) << " " << query(i, j-1) << " " << query(i+1, j) << " " << query(i+1, j-1) << '\n';
ans = (ans + C(H) * C(query(i, j)) % mod) % mod;
ans = (ans - C(H) * C(query(i, j-1)) + mod % mod) % mod;
ans = (ans - C(H) * C(query(i+1, j)) + mod % mod) % mod;
ans = (ans + C(H) * C(query(i+1, j-1)) + mod % mod) % mod;
}
}
for(int i=1; i<=n; i++) ans = (ans + C(w[i]) * C(h[i])) % mod;
cout << ans << '\n';
return 0;
}
return 0;
}
