///Enta etfsh5t nseet el rank

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update

using namespace std;
using namespace __gnu_pbds;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,
        tree_order_statistics_node_update>;
#define pb push_back
#define F first
#define S second
#define f(i, a, b) for (int i = a; i < b; i++)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define sz(x) (int)(x).size()
#define mp(x, y) make_pair(x, y)
#define popCnt(x) (__builtin_popcountll(x))
#define int ll

using ll = long long;
using ull = unsigned long long;
using uint = uint32_t;
using ii = pair<int, int>;

const int N = 1e6 + 6, A = 26, LG = 18, MOD = 1e9 + 7;
const long double PI = acos(-1);
const long double EPS = 1e-9;
const ll INF = 1e15;

void doWork() {

    int n;
    cin >> n;
    vector<int> a(n), b(n);
    f(i, 0, n) cin >> a[i];
    f(i, 0, n) cin >> b[i];
    if (accumulate(all(a), 0ll) > accumulate(all(b), 0ll)) {
        cout << "-1\n";
        return;
    }
    int lo = 0, hi = n - 1;
    while (lo < hi) {
        int md = lo + (hi - lo) / 2;
        deque<ii> dq1, dq2;
        bool ok = true;
        f(i, 0, n) {
            dq1.push_back(ii(b[i], i));
            dq2.push_back(ii(a[i], i));
            while (i - dq1.front().S > md)dq1.pop_front();
            if (i - dq2.front().S > md) {
                ok = false;
                break;
            }
            while (dq1.size() && dq2.size()) {
                int cur = min(dq1.front().F, dq2.front().F);
                dq1.front().F -= cur;
                dq2.front().F -= cur;
                if (!dq1.front().F)dq1.pop_front();
                if (!dq2.front().F)dq2.pop_front();
            }
        }
        ok &= dq2.empty();
        if (ok)
            hi = md;
        else
            lo = md + 1;

    }
    cout << lo << '\n';

}


int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE
    int t = 1;
//    cin >> t;
    while (t--)
        doWork();

    return 0;
}