#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
typedef long long LL;
typedef long long ll;
const int maxn = 5e5+100;
struct node
{
int l,r;
int maxx;
}tree[4*maxn];
int a[maxn],b[maxn];
void push_up(int i)
{
tree[i].maxx = max(tree[i<<1].maxx,tree[i<<1|1].maxx);
}
void build(int i,int l,int r)
{
tree[i].l = l,tree[i].r = r;
tree[i].maxx = 0;
if(l==r)
{
tree[i].maxx = a[l];
return ;
}
int mid = (l+r)>>1;
build(i<<1,l,mid);
build(i<<1|1,mid+1,r);
push_up(i);
}
void update(int i,int pos,int val)
{
int l = tree[i].l;
int r = tree[i].r;
if(l==pos && r==pos)
{
tree[i].maxx = val;
return ;
}
int mid = (l+r)>>1;
if(mid>=pos)
update(i<<1,pos,val);
else
update(i<<1|1,pos,val);
push_up(i);
}
int query(int i,int l,int r)
{
int L = tree[i].l;
int R = tree[i].r;
if(l<=L && R<=r)
return tree[i].maxx;
int mid = (L+R)>>1;
int ans = 0;
if(mid<r)
ans = max(ans,query(i<<1|1,l,r));
if(mid>=l)
ans = max(ans,query(i<<1,l,r));
return ans;
}
int main()
{
int n;
while(~scanf("%d",&n))
{
for(int i=1;i<=n;i++)
{
scanf("%d",&a[i]);
a[i] -= i;
}
for(int i=1;i<=n;i++)
scanf("%d",&b[i]);
sort(b+1,b+n+1);
build(1,1,2*n);
ll ans = 0,r = n;
for(int i = 1;i<=n;i++)
{
ll mm = query(1,b[i],r);
r++;
update(1,r,mm-r);
ans = (ans+mm)%1000000007;
}
printf("%I64d\n",ans);
}
return 0;
}