#include <bits/stdc++.h>
using namespace std;
#define SZ 2999999
typedef long long ll;
#define pb push_back
int n,c[SZ],a[SZ];
ll f[SZ];
ll ss[SZ];
void cmin(ll& a,ll b) {
    if(a>b) a=b;
}
struct Line {
mutable ll k, m, p;
bool operator<(const Line& o) const { return k < o.k; }
bool operator<(ll x) const { return p < x; }
};
struct LineContainer : multiset<Line, less<>> {
// ( for doubles , use inf = 1/.0, div(a, b) = a/b)
static const ll inf = LLONG_MAX;
ll div(ll a, ll b) { // floored division
return a / b - ((a ^ b) < 0 && a % b); }
bool isect(iterator x, iterator y) {
if (y == end()) return x->p = inf, 0;
if (x->k == y->k) x->p = x->m > y->m ? inf : -inf;
else x->p = div(y->m - x->m, x->k - y->k);
return x->p >= y->p;
}
void add(ll k, ll m) {
k=-k; m=-m;
auto z = insert({k, m, 0}), y = z++, x = y;
while (isect(y, z)) z = erase(z);
if (x != begin() && isect(--x, y)) isect(x, y = erase(y));
while ((y = x) != begin() && (--x)->p >= y->p)
isect(x, erase(y));
}
ll query(ll x) {
if(empty()) return 4e18;
auto l = *lower_bound(x);
return -(l.k * x + l.m);
}
};
void work(int l,int m,int r) {
    ss[m]=c[m];
    for(int i=m-1;i>=l;--i)
        ss[i]=max(ss[i+1],(ll)c[i]);
    ss[m+1]=c[m];
    for(int i=m+2;i<=r;++i)
        ss[i]=max(ss[i-1],(ll)c[i-1]);
    int j=m;
    LineContainer p;
    for(int i=m+1;i<=r;++i) {
        while(j>=l&&ss[i]>ss[j]) {
            p.add(-j,f[j]);
            --j;
        }
        cmin(f[i],p.query(ss[i])+ss[i]*i+a[i]);
    }
    p.clear();
    j=l;
    for(int i=r;i>=m+1;--i) {
        while(j<=m&&ss[i]<=ss[j]) {
            p.add(ss[j],-ss[j]*j+f[j]);
            ++j;
        }
        cmin(f[i],p.query(i)+a[i]);
    }
}
void fz(int l,int r) {
    if(l==r) return;
    int m=(l+r)>>1;
    fz(l,m);
    work(l,m,r);
    fz(m+1,r);
}
int main() {
    scanf("%d",&n);
    for(int i=0;i<=n;++i) f[i]=4e18; f[0]=0;
    for(int i=0;i<n;++i) scanf("%d",c+i);
    for(int i=1;i<n;++i) scanf("%d",a+i);
    fz(0,n);
    cout<<f[n]<<"\n";
}