#include<iostream>
#include<stdio.h>
#include<math.h>
#include<map>
#include<string>
#include<algorithm>
#include<vector>
#include<string.h>
#include<utility>
#include<set>
#include<cmath>
#include<queue>
#include<deque>
#include<functional>
#include<stack>
#include<limits.h>
#include<iomanip>
#include<unordered_map>
using namespace std;
#define MOD 1000000007
#define int long long
#define endl '\n'
int cal(int a, int b){
int f=(a*(a+1))%MOD*((MOD+1)/2)%MOD;
int s=(b*(b+1))%MOD*((MOD+1)/2)%MOD;
return (f*s)%MOD;
}
void solve(){
int n; cin>>n;
vector<int> h(n+1),w(n+1);
vector<pair<int,int> > p(n+1);
for(int i=1; i<=n; i++) cin>>h[i];
for(int i=1; i<=n; i++) cin>>w[i];
int mx=0;
int ans=0;
for(int i=1; i<=n; i++) mx=max(mx,h[i]);
for(int i=1; i<=mx; i++){
int cur=0;
for(int j=1; j<=n; j++){
if(h[j]>=i) cur=(cur+w[j])%MOD;
else{
ans=(ans+cal(cur,h[i]))%MOD;
ans=(ans-cal(cur,h[i]-1)+MOD)%MOD;
cur=0;
}
}
ans=(ans+cal(cur,h[i]))%MOD;
ans=(ans-cal(cur,h[i]-1)+MOD)%MOD;
}
cout<<ans;
}
signed main(){
// freopen("hps.in", "r", stdin);
// freopen("hps.out", "w", stdout);
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t=1;
// cin>>t;
while(t--){
solve();
cout<<endl;
}
return 0;
}
