#include <bits/stdc++.h>
/*
5
2 1 5 1 3

答案 2
*/
using namespace std;
struct Node {
    int pos;
    int step;
};
const int N = 110;
int a[N];
int st[N];
int n;
void bfs() {
    queue<Node> q;
    q.push({1, 0});
    st[1] = 1;
    while (q.size()) {
        auto t = q.front();
        q.pop();
        for (int i = 1; i <= a[t.pos]; i++) {
            int x = t.pos + i;
            // 先判断下一跳是不是终点
            if (x == n) {
                cout << t.step + 1 << endl;
                exit(0);
            }
            // 正常入队列
            if (st[x]) continue;
            q.push({x, t.step + 1});
            st[x] = 1;
        }
    }
}
int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    bfs();
    return 0;
}