/*
Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528)
*/
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define fi first
#define se second
#define __builtin_popcount __builtin_popcountll
#define all(x) (x).begin(), (x).end()
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(x) ((1ll << (x)))
#define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n';
const int MAXN = 1e5 + 5;
const int MOD = 1e9 + 7;
int n, h[MAXN], w[MAXN];
void init() {
cin >> n;
for (int i = 1; i <= n; ++i) cin >> h[i];
for (int i = 1; i <= n; ++i) cin >> w[i];
}
// x * (x - 1) / 2
int C2 (int x) {
int f1 = x, f2 = x - 1;
if (f1 % 2 == 0) f1 /= 2;
else f2 /= 2;
f1 %= MOD; f2 %= MOD;
return f1 * f2 % MOD;
}
void add(int &x, int y) {x = (x + y) % MOD;}
void sub(int &x, int y) {x = ((x - y) % MOD + MOD) % MOD;}
int cnt_sub_rects(int x, int y) {
return C2(x + 1) * C2(y + 1) % MOD;
}
namespace subtask6 {
bool check() {return n <= 1000;}
const int INF = 1e9 + 7;
void solve() {
int res = 0;
for (int i = 1; i <= n; ++i) {
int minhi = INF, len = 0;
for (int j = i; j <= n; ++j) {
minhi = min(minhi, h[j]);
len += w[i];
if (i == j)
add(res, cnt_sub_rects(minhi, len));
else {
int contrib = cnt_sub_rects(minhi, len);
sub(contrib, cnt_sub_rects(minhi, len - w[i]));
sub(contrib, cnt_sub_rects(minhi, len - w[j]));
add(contrib, cnt_sub_rects(minhi, len - w[i] - w[j]));
add(res, contrib);
}
}
}
cout << res;
}
}
signed main() {
#ifdef NCTHANH
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
init();
if (subtask6::check()) return subtask6::solve(), 0;
return 0;
}
