#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define lli long long int
#define rep(i,a,b) for (lli i = (a); i <= (b); i++)
#define repa(i,a,b) for (lli i = (a); i >= (b); i--)
#define debugsl(a) cout << #a << " = " << a << ", "
#define debug(a) cout << #a << " = " << a << endl
#define altura first
#define pos second
#define MAX 100000
#define mod 1000000007
lli n,res,ult,act,a,w,pas;
lli h[MAX+2];
stack<pair<lli,lli> > pila;
pair<lli,lli> k;
lli calcula(lli f, lli c) {
lli a = (f*(f+1))/2;
a %= mod;
lli b = (c*(c+1))/2;
b %= mod;
a *= b;
a %= mod;
return a;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
rep(i,1,n) cin >> h[i];
act = 1;
pila.push({0,0});
rep(i,1,n) {
cin >> w;
pas = act;
while (!pila.empty() && pila.top().altura > h[i]) {
k = pila.top();
pila.pop();
pas = k.pos;
a = act-k.pos;
res += calcula(a, k.altura);
res -= calcula(a, max(pila.top().altura, h[i]));
if (res < 0) res += mod;
res %= mod;
}
act += w;
if (pila.top().altura == h[i]) continue;
else (pila.push({h[i],pas}));
}
while (!pila.empty()) {
k = pila.top();
pila.pop();
if (k.altura == 0) break;
pas = k.pos;
a = act-k.pos;
res += calcula(a, k.altura);
res -= calcula(a, pila.top().altura);
if (res < 0) res += mod;
res %= mod;
}
cout << res;
}
