#include<bits/stdc++.h> typedef long long ll; #define pb push_back #define fr first #define sc second #define endl '\n' using namespace std; #define mid ((left+right)>>1) const int mod=1e9+7; int sum(int x,int y){ if(x+y<mod)return x+y; return x+y-mod; } int sub(int x,int y){ if(y)y=mod-y; return sum(x,y); } int mul(ll x,ll y){ return x*y%mod; } int cal(int x){ return mul(mul(x,sum(x,1)),500000004); } int n; int h[100023],w[100023]; int ans=0; int main(){ ios_base::sync_with_stdio(23^23);cin.tie(NULL); cin>>n; for(int i=1;i<=n;i++){ cin>>h[i]; } for(int i=1;i<=n;i++){ cin>>w[i]; } vector<pair<int,int>>sta; int val=0; for(int i=1;i<=n;i++){ int x=0; while(sta.size()&&sta.back().fr>=h[i]){ val=sub(val,mul(sta.back().sc,cal(sta.back().fr))); x=sum(x,sta.back().sc); sta.pop_back(); } if(x){ sta.pb({h[i],x}); val=sum(val,mul(x,cal(h[i]))); } ans=sum(ans,mul(val,w[i])); ans=sum(ans,mul(cal(w[i]),cal(h[i]))); x=w[i]; while(sta.size()&&sta.back().fr>=h[i]){ val=sub(val,mul(sta.back().sc,cal(sta.back().fr))); x=sum(x,sta.back().sc); sta.pop_back(); } if(x){ sta.pb({h[i],x}); val=sum(val,mul(x,cal(h[i]))); } } cout<<ans<<endl; }