#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#define tof_io ios_base::sync_with_stdio(false);cin.tie(0) , cout.tie(0);
#define double long double
#define int long long
#define pb push_back
#define all(x) x.begin(),x.end()
#define endl '\n'
const int mod = 1e9+7; //998244353
const long long inf = 1e18;
const int N = 1e3 + 23;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
int modplus(int x) {if (x >= mod) {x -= mod;} else if (x < 0) {x += mod;}return x;}
int nc2(int x){x = x * (x+1);return x;}
vector<pair<int, int>> s;
vector<int> h;
vector<int> ps;
int ans = 0;
int res = 0;
void sl(int i)
{
while (s.back().first >= h[i])
{
int x = (s.back().second - s[s.size() - 2ll].second) % mod;
res = modplus(res - x * (nc2(s.back().first) / 2 % mod) % mod);
s.pop_back();
}
}
int32_t main()
{
int n;
cin >> n;
h.pb(0);
ps.pb(0);
for (int i = 1; i <= n; i++)
{
int x;
cin >> x;
h.pb(x);
}
for (int i = 1; i <= n; i++)
{
int x;
cin >> x;
ps.pb(x + ps[i-1]);
}
s.pb(make_pair(0ll,0ll));
for (int i = 1; i <= n; i++)
{
sl(i);
if (s.back().second != ps[i-1])
{
int x = (ps[i - 1] - s.back().second) % mod;
res = modplus(res + x * (nc2(h[i]) / 2 % mod) % mod);
s.pb(make_pair(h[i], ps[i - 1]));
}
int x = (ps[i] - ps[i - 1]) % mod;
ans = modplus(ans + res % mod * x % mod);
ans = modplus(ans + (nc2(x) % nc2(mod)/2 % mod) * (nc2(h[i]) % nc2(mod)/2 % mod) % mod);
res = modplus(res + (nc2(h[i]) / 2 % mod) * x % mod);
s.pb(make_pair(h[i], ps[i]));
}
cout << ans;
}
