#include <bits/stdc++.h>
#define N 500011
#define ll long long
#define pii pair<int,int>
#define s1 first
#define s2 second
using namespace std;
int n,c[N],a[N];
struct modi{ll v,*id;}md[N*40];int mdn;
void Modi(ll &x,ll y,bool d)
{
	if(x==y)return;
	if(d){++mdn;md[mdn].v=x;md[mdn].id=&x;}
	x=y;
}
struct line
{
	ll k,b;
	line(){}line(ll _k,ll _b){k=_k;b=_b;}
	ll operator()(ll x){return k*x+b;}
};
struct sgt
{
	ll lc[N*2],rc[N*2],gn;int gb[N*2];line tr[N*2];
	sgt(){for(int i=N*2-1;i;--i)gb[++gn]=i;}
	void ins(line l,int L,int R,ll &x,bool d=0)
	{
		if(L>R)return;//printf("ins(%lldx+%lld,[%d,%d],%lld,%d)\n",l.k,l.b,L,R,x,d);
		if(!x)
		{
			Modi(x,gb[gn],d);
			Modi(gn,gn-1,d);
			tr[x]=l;lc[x]=rc[x]=0;
			return;
		}
		int mid=L+R>>1;
		if(l(mid)<=tr[x](mid))
		{
			line tt=tr[x];
			Modi(tr[x].k,l.k,d);
			Modi(tr[x].b,l.b,d);
			l=tt;
		}
		if(l.k<tr[x].k)ins(l,(L+R>>1)+1,R,rc[x],d);
		else ins(l,L,L+R>>1,lc[x],d);
	}
	ll query(int X,int L,int R,int x)
	{//printf("query(%d,[%d,%d],%d) (%lldx+%lld)\n",X,L,R,x,tr[x].k,tr[x].b);
		if(!x)return 1e18;
		if(L==R)return tr[x](X);
		ll ans=tr[x](X);
		if(X<=L+R>>1)return min(ans,query(X,L,L+R>>1,lc[x]));
		else return min(ans,query(X,(L+R>>1)+1,R,rc[x]));
	}
	int merge(ll x,int y,int L,int R)
	{//printf("merge(%lld,%d,[%d,%d])\n",x,y,L,R);
		if(!x||!y)return x^y;
		lc[x]=merge(lc[x],lc[y],L,L+R>>1);
		rc[x]=merge(rc[x],rc[y],(L+R>>1)+1,R);
		gb[++gn]=y;ins(tr[y],L,R,x);
		return x;
	}
}T1,T2;
pii mx[21][N];
ll f[N];int lg[N];
pii query(int l,int r)
{
	int logl=lg[r-l+1];
	return max(mx[logl][l],mx[logl][r-(1<<logl)+1]);
}
int lc[N*2],rc[N*2],sz;ll rt1[N*2],rt2;
void solve(int L,int R,int &x)
{
	if(!x)x=++sz;
	// printf("solve([%d,%d],%d)\n",L,R,x);
	if(L==R)
	{
		if(L)f[L]=T2.query(L,0,n,1)+a[L];
		T1.ins(line(-L,f[L]),-1e9,-1,rt1[x]);
		return;
	}
	int tmdn=mdn;
	int M=query(L,R-1).s2;
	solve(L,M,lc[x]);
	int c=::c[M];
	ll val=T1.query(c,-1e9,-1,rt1[lc[x]]);
	// printf("[%d,%d] M:%d c:%d val:%lld\n",L,R,M,c,val);
	T2.ins(line(c,val),1,n,rt2,1);
	solve(M+1,R,rc[x]);
	rt1[x]=T1.merge(rt1[lc[x]],rt1[rc[x]],-1e9,-1);//printf("rt1[%d,%d]:%d\n",L,R,rt1[x]);
	while(mdn>tmdn)*md[mdn].id=md[mdn].v,--mdn;
}
int rt;
int main()
{
	// freopen("O.in","r",stdin);freopen("O.out","w",stdout);setvbuf(stdout,0,_IONBF,0);
	scanf("%d",&n);
	for(int i=0;i<n;++i)scanf("%d",c+i);
	for(int i=1;i<n;++i)scanf("%d",a+i);
	for(int i=0;i<n;++i)mx[0][i]=pii(c[i],i);
	for(int i=1;i<=20;++i)for(int j=0;j+(1<<i)-1<n;++j)mx[i][j]=max(mx[i-1][j],mx[i-1][j+(1<<i-1)]);
	lg[0]=-1;for(int i=1;i<=n;++i)lg[i]=lg[i>>1]+1;
	solve(0,n,rt);
	// printf("f:");for(int i=0;i<=n;++i)printf("%lld ",f[i]);putchar(10);
	printf("%lld\n",f[n]);
	fclose(stdin);fclose(stdout);return 0;
}