#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pb push_back
const int M=1e9+7;
const int two=500000004; //modinv
int n, h[100001], w[100001];
int dp[100001], prf[100001];
int mul(int a, int b){a%=M; b%=M; return (a*b)%M;}
int add(int a, int b){a%=M; b%=M; return (a+b+M)%M;}
int nc2(int x){return mul(mul(x,x-1),two);}
signed main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr);
cin >> n;
for(int i=1;i<=n;i++) cin >> h[i];
for(int i=1;i<=n;i++) cin >> w[i], prf[i]=prf[i-1]+w[i];
stack<int> mn; //smaller to left of i
for(int i=1;i<=n;i++){
while(!mn.empty() && mn.top()>=h[i]) mn.pop();
if(mn.empty()) dp[i]=mul(nc2(h[i]+1), nc2(w[i]+1));
else{
int x=prf[i]-prf[mn.top()];
dp[i]=mul(nc2(x+1), nc2(h[i]+1));
dp[i]=add(dp[i], mul(dp[mn.top()], w[i]));
}
mn.push(i);
}
int ans=0;
for(int i=1;i<=n;i++) ans=add(ans,dp[i]);
cout << ans << '\n';
}
