#include <bits/stdc++.h>
#define fi first
#define se second
#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define REP(i,a,b) for(int i=(a); i>=(b); --i)
#define umax(x, y) x = max(x, (y))
#define umin(x, y) x = min(x, (y))
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(i) (1LL << (i))
#define sz(v) (int)(v).size()
#define ALL(v) (v).begin(),(v).end()
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const int N = 1e6 + 5;
const int mod = 1e9 + 7;
const int base = 311;
const ll INF = 1e18;
void add(int &a, int b) { a += b; if (a >= mod) a -= mod; }
int sub(int a, int b) { a -= b; if (a < 0) a += mod; return a; }
int mul(int a, int b) { return 1ll * a * b % mod; }
// Author: rexdino
int n, h[N], w[N];
int inv2, ans;
int binpow(int a, int b){
int res = 1;
while(b){
if (b & 1) res = mul(res, a);
a = mul(a, a);
b >>= 1;
}
return res;
}
int C2(int n){
return mul(mul(n, n + 1), inv2);
}
namespace sub26{
void solve(){
FOR(i, 1, n) FOR(j, i + 1, n){
}
}
}
namespace sub2{
bool check(){
FOR(i, 1, n) if (w[i] != i) return 0;
return n <= 50;
}
void solve(){
int ans = 0;
FOR(i, 1, n){
int mn = mod;
FOR(j, i, n){
umin(mn, h[j]);
add(ans, C2(mn));
}
}
cout << ans;
}
}
namespace sub3{
bool check(){
FOR(i, 1, n) if (h[i] != 1 && h[i] != 2) return 0;
return 1;
}
void solve(){
FOR(i, 1, n){
if (h[i] == 2){
int j = i;
while(h[j + 1] == 2 && j < n) j++;
add(ans, mul(2, C2(sub(w[j], w[i - 1]))));
i = j;
}
}
add(ans, C2(w[n]));
cout << ans;
}
}
namespace sub4{
bool check(){
FOR(i, 2, n) if (h[i] != h[i - 1]) return 0;
return 1;
}
void solve(){
ans = mul(C2(h[1]), C2(w[n]));
cout << ans;
}
}
namespace sub5{
bool check(){
FOR(i, 2, n) if (h[i] < h[i - 1]) return 0;
return 1;
}
void solve(){
FOR(i, 1, n){
int j = i;
while(h[j + 1] == h[i] && j < n) j++;
int k = h[i] - h[i - 1];
add(ans, mul(C2(k), C2(sub(w[n], w[i - 1]))));
add(ans, mul(mul(k, h[i - 1]), C2(sub(w[n], w[i - 1]))));
// cerr << ans << "\n";
i = j;
}
cout << ans;
}
}
namespace sub6{
int val[N];
void solve(){
FOR(i, 1, n) val[i] = sub(w[i], w[i - 1]);
FOR(i, 1, n){
int mn = h[i];
// cerr << ans << "\n";
add(ans, mul(C2(val[i]), C2(h[i])));
// cerr << i << ": " << ans << "\n";
FOR(j, i + 1, n){
umin(mn, h[j]);
add(ans, mul(mul(val[i], val[j]), C2(mn)));
}
}
cout << ans;
}
}
// namespace subfull{
// void solve(){
// }
// }
void solve(){
cin >> n;
FOR(i, 1, n) cin >> h[i];
FOR(i, 1, n) cin >> w[i], add(w[i], w[i - 1]);
inv2 = binpow(2, mod - 2);
if (sub4::check()) return sub4::solve();
if (sub3::check()) return sub3::solve();
if (sub5::check()) return sub5::solve();
if (sub2::check()) return sub2::solve();
if (n <= 1000) return sub6::solve();
}
signed main(){
#define NAME "main"
if (fopen(NAME".inp", "r")){
freopen(NAME".inp", "r", stdin);
freopen(NAME".out", "w", stdout);
}
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int t = 1;
// cin >> t;
while(t--) solve();
// cerr << "Time elapsed: " << (1.0 * clock() / CLOCKS_PER_SEC) << "s\n";
return 0;
}
