#include <iostream>
#include <vector>
#include <queue>
using namespace std;

class Solution {
public:
    typedef pair<int, int> P; // {last date before expiration, number of apples}
    int eatenApples(vector<int>& apples, vector<int>& days) {
        int ans = 0, n = apples.size();
        // min heap, the pair with the smallest expiration date is on the top
        priority_queue<P, vector<P>, greater<P>> que;
        int i = 0;
        while(i < n || !que.empty()){
            // add today's apples
            if(i < n && apples[i] > 0) que.push({i + days[i] - 1, apples[i]});
            // remove outdate apples
            while(!que.empty() && que.top().first < i) que.pop();
            // get the apple that can be eat today
            if(!que.empty()){
                auto p = que.top();
                que.pop();
                if(p.second > 1) que.push({p.first, p.second - 1});
                ++ans;
            }
            ++i;
        }
        return ans;
    }
};

int main() {
    // Read input from file
    freopen("input.txt", "r", stdin);
    int n;
    cin >> n;
    vector<int> apples(n), days(n);
    for(int i = 0; i < n; ++i) {
        cin >> apples[i];
    }
    for(int i = 0; i < n; ++i) {
        cin >> days[i];
    }
    fclose(stdin);

    // Solve problem and print output
    Solution sol;
    int ans = sol.eatenApples(apples, days);
    cout << ans << endl;

    return 0;
}