#include <bits/stdc++.h>
using namespace std;
using vi = basic_string<int>;
#define all(v) (v).begin(), (v).end()
#define bs(v, x) upper_bound(all(v), x) - (v).begin()
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
cin >> n;
vi x(n, 0), y(n, 0), yl, xp(n, 0);
for(int i=0; i<n; i++){
cin >> x[i];
if(i){
xp[i] = xp[i-1];
}
xp[i] += x[i];
}
for(int i=0; i<n; i++){
cin >> y[i];
for(int j=0; j<y[i]; j++){
yl += i;
}
}
deque<int> v1, v2;
int cur = 0;
for(int i=0; i<yl.size(); i++){
int t = bs(xp, i);
int& s = yl[i];
if(t < s){
cur++;
}
else if(t == s){
v1.push_back(i);
}
else{
v2.push_back(i);
cur--;
}
}
int ans = cur;
int ft = bs(xp, 0);
for(int i=1; i<yl.size(); i++){
if(ft < yl[i-1]){
cur -= 2;
}
else if(ft == yl[i-1]){
cur -= 1;
}
else{
break;
}
if(bs(xp, yl.size()-1) < yl[i-1]){
cur += 2;
}
if(bs(xp, yl.size()-1) == yl[i-1]){
cur += 1;
}
while(v2.size() && v2.front() < i){
v2.pop_front();
}
while(v2.size() && bs(xp, v2.front() - i) <= yl[v2.front()]){
cur++;
v1.push_back(v2.front());
v2.pop_front();
}
while(v1.size() && v1.front() < i){
v1.pop_front();
}
while(v1.size() && bs(xp, v1.front() - i) < yl[v1.front()]){
cur++;
v1.pop_front();
}
if(cur > ans){
ans = cur;
}
}
cout << ans;
return 0;
}
