This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define pii pair<ll,ll>
#define REP(i,x,y) for(ll i=x;i<=y;i++)
#define freeopen freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
#define mod 1000000007
#define pb push_back
#define mk make_pair
#define ll long long
#define foor(x,vec) for(auto x:vec ){cout<<x<<" ";}
#define fi first
#define se second
#define MAXN 700069
#define lld long double
#define cha ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ffl fflush(stdout)
#define sst string
#define pii pair<ll,ll>
ll mvx[]={0,0,-1,1};
ll mvy[]={1,-1,0,0};
ll n,q;
ll a,b;
ll h[MAXN],w[MAXN];
ll ps[MAXN];
ll dp[MAXN];
ll idx[MAXN];
int main(){
cin>>n;
REP(i,1,n)cin>>h[i];
REP(i,1,n)cin>>w[i];
REP(i,1,n){
ps[i]=ps[i-1]+w[i];
}
stack <ll> stck;
stck.push(0);
REP(i,1,n){
while(stck.size() && h[i]<stck.top()){
stck.pop();
}
idx[i]=stck.top();
stck.push(h[i]);
}
ll ans=0;
REP(i,1,n){
ll val=dp[idx[i]]*(ps[i]-ps[idx[i]]);
val%=mod;
dp[i]=dp[idx[i]]+((h[i]*(h[i]+1)/2)%mod*(ps[i]-ps[idx[i]]))%mod;
dp[i]%=mod;
val=val+(((h[i]*(h[i]+1)/2)%mod)*((w[i])*(w[i]+1))/2)%mod;
val%=mod;
ans+=val;
ans%=mod;
}
cout<<ans<<endl;
}
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