#pragma GCC optimize("Ofast,inline,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
// #define TXT
#define FILENAME ""
#ifdef TXT
struct FileOpener {
FileOpener() {
freopen(FILENAME".in", "r", stdin);
freopen(FILENAME".out", "w", stdout);
}
} fileopener;
#endif
using ll = int64_t;
using ull = uint64_t;
using vi = vector<ll>;
using vvi = vector<vector<ll>>;
using ii = pair<ll,ll>;
using vii = vector<ii>;
using vvii = vector<vector<ii>>;
#define fore(i,b,e) for (int64_t i = (b); i < (e); ++i)
#define foree(i,b,e) for (int64_t i = (b); i <= (e); ++i)
#define ford(i,b,e) for (int64_t i = (e)-1; i >= (b); --i)
#define fordd(i,b,e) for (int64_t i = (e); i >= (b); --i)
#define ff first
#define ss second
#define pb push_back
#define pob pop_back
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define fastIO ios::sync_with_stdio(false)
#define ceilll(n,d) (((n)+(d)-1)/(d))
#define print_arr(arr,b,e) {fore(i,(b),(e)) cout << arr[i] << ' '; cout << '\n';}
#define id(x) #x
const double PI = 3.1415926535897932;
const double EPS = 1e-9;
constexpr ll INF = 1e18;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// Memory measurement: command time -f '\nTime: %e s Memory: %M KB' ./exe
inline ull gcd(ull a, ull b) {
while (a&&b)
a>b?a%=b:b%=a;
return a?a:b;
}
inline ull lcm(ull a, ull b) {
return a/gcd(a,b)*b;
}
inline ull power(ull a, ll b) {
ull ans = 1;
while (b) {
if (b&1) ans *= a;
a *= a;
b >>= 1;
}
return ans;
}
inline ull powmod(ull a, ll b, ull _mod) {
ull ans = 1;
a %= _mod;
while (b) {
if (b&1) ans = (ans * a) % _mod;
a = (a * a) % _mod;
b >>= 1;
}
return ans;
}
ll phi(ll n) {
ll m;
m = n;
for(ll i = 2; i*i <= m; ++i) {
if (m % i == 0) {
n = n/i*(i-1);
while (m % i == 0)
m /= i;
}
}
if (m != 1)
n = n/m*(m-1);
return n;
}
ull phi(ull n) {
ull m;
m = n;
for(ull i = 2; i*i <= m; ++i) {
if (m % i == 0) {
n = n/i*(i-1);
while (m % i == 0)
m /= i;
}
}
if (m != 1)
n = n/m*(m-1);
return n;
}
inline ull num_of_digits(ull n) {
ll ans = 0;
while (n) {
n /= 10;
++ans;
}
return ans;
}
inline ull num_of_digits_b(ull n) {
ll ans = 0;
while (n) {
n >>= 1;
++ans;
}
return ans;
}
bool is_prime(ll n) {
for (ll i = 2; i*i <= n; ++i)
if (n % i == 0) return false;
return true;
}
ull mr_mult_mod(ull a, ull b, ull mod) {
ull ans = 0;
while (b) {
if (b&1) ans = (ans+a) % mod;
a = (a << 1) % mod;
b >>= 1;
}
return ans;
}
ull mr_pow_mod(ull a, ull p, ull mod) {
ull ans = 1;
while (p) {
if (p&1) ans = mr_mult_mod(ans, a, mod);
a = mr_mult_mod(a, a, mod);
p >>= 1;
}
return ans;
}
bool miller_rabin(ull n) {
if (n == 2)
return true;
if (n < 2 || n % 2 == 0)
return false;
ull nn = n-1;
ull s = 0, d;
while (nn % 2 == 0)
++s, nn /= 2;
d = nn;
const vector<ull> primes{2,3,5,7,11,13,17,19,23,29,31,37};
for (ull a : primes) {
if (a == n) return true;
ull x = mr_pow_mod(a, d, n);
ull y;
fore(i, 0, s) {
y = mr_mult_mod(x, x, n);
if (y == 1 && x != 1 && x != n-1)
return false;
x = y;
}
if (y != 1)
return false;
}
return true;
}
////////////////////////////////////////////
// SOLUTION //
// #define MULTITEST
// #define GENERATE_TEST
// #define CHECK_ANSWER
void precalc() {
}
struct seg {
ll l,r,h;
bool operator<(const seg &o) const {
return h > o.h;
}
};
const ll mod = 1000000007;
ll cn2(ll n) {
n %= mod;
return n*(n+1)/2%mod;
}
void solve() {
ll n; cin >> n;
vi h(n), w(n);
vector<seg> s(n);
ll x = 0;
fore(i,0,n) cin >> h[i];
fore(i,0,n) {
cin >> w[i];
s[i] = {x, x+w[i], h[i]};
x += w[i];
}
s.pb({-1,-1,0});
sort(all(s));
ll ans = 0, last = -1;
set<ii> segs;
ll sum = 0;
auto insert = [&](ll l, ll r) {
auto nit = segs.lower_bound({l,r});
auto pit = segs.end();
if (nit != segs.begin()) pit = prev(nit);
if (nit != segs.end() && nit->ff == r) {
(sum += mod - cn2(nit->ss - nit->ff)) %= mod;
r = nit->ss;
segs.erase(nit);
}
if (pit != segs.end() && pit->ss == l) {
(sum += mod - cn2(pit->ss - pit->ff)) %= mod;
l = pit->ff;
segs.erase(pit);
}
(sum += cn2(r - l)) %= mod;
segs.insert({l,r});
};
for (const auto &[l,r,h] : s) {
if (h != last) {
(ans += sum * (cn2(last) - cn2(h) + mod) % mod) %= mod;
}
insert(l,r);
last = h;
}
cout << ans << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0), cout.tie(0);
cout.precision(12);
precalc();
#ifdef MULTITEST
ll t;
cin >> t;
while (t--)
#endif
solve();
return 0;
}
