#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
using namespace std;
const int MAX=3e5+5;
const ll INF=1LL<<60;
int N;
ll X[MAX],Y[MAX];
ll A[MAX],B[MAX];
ll calc(ll x){
copy(X,X+N,A),copy(Y,Y+N,B);
ll ans=-x;
int i=0,j=N-1;
while (x){
while (!A[i]) i++;
while (!B[j]) j--;
ll c=min(x,min(A[i],B[j]));
x-=c,A[i]-=c,B[j]-=c;
}
i=0,j=0;
while (i<N){
while (i<N&&!A[i]) i++;
if (i>=N) break;
while (!B[j]) j++;
ll c=min(A[i],B[j]);
A[i]-=c,B[j]-=c;
if (j>i) ans-=c;
if (j<i) ans+=c;
}
return ans;
}
int main(){
cin>>N;
for (int i=0;i<N;i++) cin>>Y[i];
for (int i=0;i<N;i++) cin>>X[i];
ll l=0,r=0;
for (int i=0;i<N;i++) r+=X[i];
while (r-l>=3){
ll m0=l+(r-l)/3;
ll m1=r-(r-l)/3;
ll v0=calc(m0),v1=calc(m1);
if (v0>v1) r=m1;
else l=m0;
}
ll ans=-INF;
for (int x=l;x<=r;x++) ans=max(ans,calc(x));
cout<<ans<<'\n';
}
