#include <bits/stdc++.h>
#define MOD 1000000007
using namespace std;
//ifstream in("intrare.in");
//ofstream out("iesire.out");
long long n,h[100010],w[100010],ans,addans;
stack<pair<long long,long long>>a;
int main()
{
cin>>n;
a.push({0,0});
for(int i=1;i<=n;++i)
cin>>h[i];
for(int i=1;i<=n;++i)
{
cin>>w[i];
w[i]+=w[i-1];
}
for(int i=1;i<=n;++i)
{
while(a.top().first>=h[i])
{
long long ws=a.top().second;
long long hs=a.top().first;
a.pop();
if(hs%2==0)
addans-=(ws-a.top().second)%MOD*hs/2%MOD*(hs+1)%MOD;
else
addans-=(ws-a.top().second)%MOD*hs%MOD*(hs+1)/2%MOD;
if(addans<0)
addans+=MOD;
}
long long sg;
if((w[i]-w[i-1])%2==0)
sg=(w[i]-w[i-1])/2%MOD*((w[i]-a.top().second+w[i-1]+1-a.top().second)%MOD)%MOD;
else
sg=(w[i]-w[i-1])%MOD*((w[i]-a.top().second+w[i-1]+1-a.top().second)/2%MOD)%MOD;
if(h[i]%2==0)
{
ans+=(addans*((w[i]-w[i-1])%MOD)+sg*h[i]/2%MOD*(h[i]+1)%MOD)%MOD;
if(ans>=MOD)
ans-=MOD;
addans+=(w[i]-a.top().second)%MOD*h[i]/2%MOD*(h[i]+1)%MOD;
if(addans>=MOD)
addans-=MOD;
}
else
{
ans+=(addans*((w[i]-w[i-1])%MOD)+sg*h[i]%MOD*(h[i]+1)/2%MOD)%MOD;
if(ans>=MOD)
ans-=MOD;
addans+=(w[i]-a.top().second)%MOD*h[i]%MOD*(h[i]+1)/2%MOD;
if(addans>=MOD)
addans-=MOD;
}
a.push({h[i],w[i]});
//out<<ans<<'\n';
}
cout<<ans;
return 0;
}
