#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back

const ll inf=9e18;
const int N=500050;
int a[N],c[N];
ll dp[N],bdp[N];

struct Line{
    ll k,n;
    Line(){}
    Line(ll a,ll b):k(a),n(b){}
    ll Get(ll x){
        return x*k+n;
    }
};

ll sec(Line a,Line b){
    ll dk=a.k-b.k;
    ll dn=b.n-a.n;
    if(dk<0)dk=-dk,dn=-dn;
    if(dn<0)return dn/dk;
    else return (dn+dk-1)/dk;
}

vector<int> hullIds;
vector<Line> hull;
void ExtendHull(int idx,Line line){
    int sz=hull.size();
    while(sz>=2 && sec(hull[sz-2],hull[sz-1])>=sec(hull[sz-1],line)){
        hull.pop_back();
        hullIds.pop_back();
        sz--;
    }
    hull.pb(line);
    hullIds.pb(idx);
}
int FindBot(int l,int r){
    int top=(int)hull.size()-1;
    int bot=0;
    int ans=(int)hull.size()-1;
    while(top>=bot){
        int mid=top+bot>>1;
        if(hullIds[mid]>=l){
            ans=mid;
            top=mid-1;
        }else{
            bot=mid+1;
        }
    }
    return ans;
}
Line GetLine(int l,int r,ll x){
    int top=(int)hull.size()-2;
    int bot=FindBot(l,r);
    int best=top+1;
    while(top>=bot){
        int mid=top+bot>>1;
        if(hull[mid].Get(x)<hull[mid+1].Get(x)){
            best=mid;
            top=mid-1;
        }else{
            bot=mid+1;
        }
    }
    return Line(x,hull[best].Get(x));
}

const int L=20;
const int M=N*L;
int ls[M],rs[M],tsz;
Line line[M];
bool has[M];

void Copy(int&c){
    ++tsz;
    ls[tsz]=ls[c];
    rs[tsz]=rs[c];
    line[tsz]=line[c];
    has[tsz]=has[c];
    c=tsz;
}

void AddLine(int &c,int ss,int se,Line l){
    Copy(c);
    if(!has[c]){
        line[c]=l;
        has[c]=true;
        return;
    }
    ll A=line[c].Get(ss);
    ll B=l.Get(ss);
    ll C=line[c].Get(se);
    ll D=l.Get(se);
    if(A<=B && C<=D)return;
    if(A>=B && C>=D){
        line[c]=l;
        return;
    }
    if(A>B)swap(l,line[c]);
    int mid=ss+se>>1;
    if(line[c].Get(mid)<=l.Get(mid))AddLine(rs[c],mid+1,se,l);
    else{
        swap(l,line[c]);
        AddLine(ls[c],ss,mid,l);
    }
}

ll Get(int c,int ss,int se,int qi){
    if(!has[c])return inf;
    ll ans=line[c].Get(qi);
    if(ss==se)return ans;
    int mid=ss+se>>1;
    if(qi<=mid)ans=min(ans,Get(ls[c],ss,mid,qi));
    else ans=min(ans,Get(rs[c],mid+1,se,qi));
    return ans;
}

int main(){
    int n;
    scanf("%i",&n);
    for(int i=1;i<=n;i++){
        scanf("%i",&c[i]);
    }
    for(int i=2;i<=n;i++){
        scanf("%i",&a[i]);
    }
    n++;
    dp[1]=0;
    bdp[1]=0;
    vector<int> roots;
    vector<int> stk;
    stk.push_back(1);
    roots.push_back(0);
    ExtendHull(1,Line(-1,0));
    for(int i=2;i<=n;i++){
        while(stk.size()>1 && c[stk.back()-1]<=c[i-1]){
            stk.pop_back();
            roots.pop_back();
        }
        int newRoot=roots.back();
        Line line=GetLine(stk.back(),i-1,c[i-1]);
        //printf("AddLine (%i * x + %i) [%i, %i]\n",line.k,line.n,stk.back(),i-1);
        AddLine(newRoot,1,n,line);
        stk.pb(i);
        roots.pb(newRoot);

        dp[i]=Get(newRoot,1,n,i)+a[i];
        ExtendHull(i,Line(-i,dp[i]));


        // Brute
        /*int mx=0;
        bdp[i]=inf;
        for(int j=i-1;j>=1;j--){
            mx=max(mx,c[j]);
            bdp[i]=min(bdp[i],bdp[j]+(ll)mx*(i-j)+a[i]);
        }
        printf("(dp:%lld bdp:%lld)\n",dp[i],bdp[i]);
        for(int j=0;j<hull.size();j++){
            printf("%i (%i * x + %i)\n",hullIds[j],hull[j].k,hull[j].n);
        }*/
    }
    printf("%lld\n",dp[n]);
    return 0;
}