#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;
const int N = 1e6 + 5;
int n, a[N], b[N];
bool check(int x) {
	vector<int> va, vb;
	for(int i = 0;i < n;i++) {
		va.push_back(a[i]);
		vb.push_back(b[i]);
	}
	int i = 0, j = 0;
	while(i < n) {
		while(j < n && abs(i - j) > x)
			j++;
		if(j == n)
			return false;
		int mn = min(va[i], vb[j]);
		va[i] -= mn, vb[j] -= mn;
		if(va[i] == 0)
			i++;
		if(vb[j] == 0)
			j++;
	}
	return true;
}
int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n;
    ll sum_a = 0, sum_b = 0;
    for(int i = 0;i < n;i++) {
		cin >> a[i];
		sum_a += a[i];
	}
	for(int i = 0;i < n;i++) {
		cin >> b[i];
		sum_b += b[i];
	}
	if(sum_a > sum_b)
		return cout << -1, 0;
	int low = 0, high = n - 1, mid, ans = -1;
	while(low <= high) {
		mid = low + high >> 1;
		if(check(mid))
			ans = mid, high = mid - 1;
		else
			low = mid + 1;
	}
	cout << ans;
    return 0;
}