#include <bits/stdc++.h>
#define ll long long
using namespace std;
int n;
ll price[101010];
ll dist[101010];
ll next_small[101010];
ll total;
int main()
{
cin >> n;
for (int i = 1; i<n; i++)
{
ll x;
cin >> x;
dist[i] = dist[i-1] + x;
}
dist[n] = dist[n-1];
for (int i = 0; i<n; i++)
cin >> price[i];
int l = 0, r = 0;
while(l < n)
{
while(price[l] <= price[r])
r++;
for (int i = l; i<r; i++)
next_small[i] = r;
l = r;
}
for (int i = 0; i<n;)
{
total += (dist[next_small[i]]-dist[i])*price[i];
i = next_small[i];
}
cout << total;
}
