#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
const int N = (int) 1e6 + 7;
const int M = (int) 1e9 + 7;
int h[N], w[N], sp[N], st[N];
int add(int a, int b) {
a += b;
a %= M;
return a;
}
int mul(int a, int b) {
return (ll) a * b % M;
}
int gauss(int a) {
return ((ll) a * (a + 1) / 2) % M;
}
int get(int x, int y) {
return mul(gauss(x), gauss(y));
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n;
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> h[i];
}
for (int i = 1; i <= n; i++) {
cin >> w[i];
sp[i] = sp[i - 1] + w[i];
}
h[n + 1] = 0;
w[n + 1] = 0;
sp[n + 1] = sp[n] + w[n + 1];
n++;
int vf = 0;
ll ret = 0;
for (int i = 1; i <= n; i++) {
while (vf > 0 && h[i] <= h[st[vf]]) {
int l = sp[i - 1] - sp[st[vf - 1]];
ret = add(ret, get(h[st[vf]], l));
ret = add(ret, -1 * get(max(h[st[vf - 1]], h[i]), l));
vf--;
}
st[++vf] = i;
}
ret += M;
ret %= M;
cout << ret;
return 0;
}
