#pragma GCC optimize("O3,inline")
#include <bits/stdc++.h>
using namespace std;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N, a, ans = 0, crnt = 0, ee = 0; cin >> N;
vector<int> X, Y, pX = { 0 }, pY = { 0 }, cX, cY;
for (int i = 0; i < N; i++) {
cin >> a;
X.push_back(a);
pX.push_back(a);
}
for (int i = 0; i < N; i++) {
cin >> a;
Y.push_back(a);
pY.push_back(a);
}
cX = X, cY = Y;
int idx = 0;
for (int i = 0; i < N; i++) {
while (cY[i] > cX[idx]) {
if (idx < i) ans += cX[idx];
else if (idx > i) ans -= cX[idx];
cY[i] -= cX[idx++];
}
if (idx < i) ans += cY[i];
else if (idx > i) ans -= cY[i];
cX[idx] -= cY[i];
}
for (int i = 1; i <= N; i++) pX[i] += pX[i - 1], pY[i] += pY[i - 1];
vector<pair<int, int>> deltas;
for (int i = 0; i < N; i++) {
auto iter1 = upper_bound(pY.begin(), pY.end(), pX[i]);
auto iter2 = upper_bound(pY.begin(), pY.end(), pX[i + 1]);
if (iter1 - pY.begin() <= i + 1 && i != 0) deltas.push_back({ max(0, pY[i] - pX[i]), 1 }), deltas.push_back({ max(0, pY[i + 1] - pX[i]), -1 });
if (iter2 - pY.begin() <= i + 1) deltas.push_back({ max(0, pY[i] - pX[i + 1]), 1 }), deltas.push_back({ max(0, pY[i + 1] - pX[i + 1]), -1 });
}
crnt = ans;
sort(deltas.begin(), deltas.end());
auto iter = deltas.begin();
for (int i = 0; iter != deltas.end(); i++) {
while (iter != deltas.end() && iter->first <= i) {
ee += iter->second;
iter++;
}
crnt -= ee + 1 + (i >= Y[0]);
ans = max(ans, crnt);
}
cout << ans << '\n';
}
