#include <bits/stdc++.h>
using namespace std;
int f(int k, vector<int> x, vector<int> y){
int ix=0, iy=0, n = x.size();
int pos = 0, neg = k;
while (k>0){
if(y[iy]==0){
iy++;
continue;
}
int c = min(k, y[iy]);
k-=c;
y[iy]-=c;
}
while(iy<n){
if(y[iy]==0){
iy++;
continue;
}
if(x[ix]==0){
ix++;
continue;
}
int c = min(y[iy], x[ix]);
x[ix]-=c;
y[iy]-=c;
if(ix<iy)pos+=c;
if(ix>iy)neg+=c;
}
return pos-neg;
}
signed main(){
int n; cin >> n;
vector<int> x(n), y(n);
for(int i=0; i<n; i++)cin >> x[i];
for(int i=0; i<n; i++)cin >> y[i];
if(n==1)cout << 0 << endl;
else{
int k=0;
for(auto it: y)k+=it;
int l=0, r= k;
while (l<r){
int m = (l+r)/2;
//cout << l << " "<< m << " "<<r << " "<< f(m, x, y)<< endl;
int vo = f(m+1, x, y)-f(m, x, y);
if(vo<0)r = m-1;
else if(vo==0) l = m, r = m;
else l = m;
}
cout << f(l, x, y);
}
}
