#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using i128=__int128;
const int N=5e5;
const ll inf=1ll<<60;
int n;
int c[N+5],a[N+5];
ll f[N+5];
struct Line{
    ll k,b;
    Line(ll k=0,ll b=0):k(k),b(b){}
    ll eval(ll x){ return k*x+b; }
}line[N+5];
bool chk1(Line x,Line y,Line z){
    return (i128)(z.k-x.k)*(x.b-y.b)<=(i128)(y.k-x.k)*(x.b-z.b);
}
bool chk2(Line x,Line y,Line z){
    return (i128)(x.k-z.k)*(y.b-x.b)>=(i128)(x.k-y.k)*(z.b-x.b);
}
void solve(int l,int r){
    if(l==r){
        f[l]+=a[l];
        return;
    }
    int mid=l+r>>1;
    solve(l,mid);
    static int pre[N+5],suf[N+5];
    suf[mid]=0; pre[mid]=0;
    for(int i=mid-1;i>=l;i--)
        suf[i]=max(suf[i+1],c[i+1]);
    for(int i=mid+1;i<=r;i++)
        pre[i]=max(pre[i-1],c[i]);
    static Line s[N+5];
    int sr=0;
    for(int i=l;i<=mid;i++)
        line[i]=Line(suf[i],f[i]-1ll*i*suf[i]);
    for(int i=r,j=l;i>mid;i--){
        while(j<=mid&&suf[j]>=pre[i]){
            while(sr>1&&chk1(line[j],s[sr],s[sr-1])) sr--;
            s[++sr]=line[j]; j++;
        }
        while(sr>1&&s[sr].eval(i)>=s[sr-1].eval(i)) sr--;
        if(sr) f[i]=min(f[i],s[sr].eval(i));
    }
    for(int i=l;i<=mid;i++)
        line[i]=Line(-i,f[i]);
    sr=0;
    for(int i=mid+1,j=mid;i<=r;i++){
        while(j>=l&&suf[j]<pre[i]){
            while(sr>1&&chk2(line[j],s[sr],s[sr-1])) sr--;
            s[++sr]=line[j]; j--;
        }
        while(sr>1&&s[sr].eval(pre[i])>=s[sr-1].eval(pre[i])) sr--;
        if(sr) f[i]=min(f[i],s[sr].eval(pre[i])+1ll*i*pre[i]);
    }
    solve(mid+1,r);
}
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        scanf("%d",&c[i]);
    for(int i=1;i<n;i++)
        scanf("%d",&a[i]);
    fill(f+1,f+1+n,inf);
    solve(0,n);
    printf("%lld\n",f[n]);
    return 0;
}