Wrath

## 题目描述 那手上流着无辜之人的血的罪人啊！ 有n个罪犯排成一排，其中第i个人拿着一个长 $L_{i}$ 的爪子。铃声敲响时每个人都会将其前面的一些人杀掉。所有人在同一时刻杀掉其他人。也就是说，如果$j<i$ 并且$j>=i-L_{i}$ ，那么第i个人将会杀掉第$j$ 个人。 现在给出每个爪子的长度，你要找出铃响之后还有多少人幸存。 ## 输入输出格式 ### 输入格式： 第一行包括一个整数$n$ $(1<=n<=10^6)$ 。 第二行包括$n$ 个整数$L_{1},L_{2},...,L_{n}(0<=L_{i}<=10^9)$ ### 输出格式： 输出一个整数，表示幸存的人的个数 ## 说明 第一个样例中，最后一个人杀掉他前面所有的人。 感谢@二元长天笑 提供的翻译

Hands that shed innocent blood! There are $ n $ guilty people in a line, the $ i $ -th of them holds a claw with length $ L_{i} $ . The bell rings and every person kills some of people in front of him. All people kill others at the same time. Namely, the $ i $ -th person kills the $ j $ -th person if and only if $ j<i $ and $ j>=i-L_{i} $ . You are given lengths of the claws. You need to find the total number of alive people after the bell rings.

The first line contains one integer $ n $ ( $ 1<=n<=10^{6} $ ) — the number of guilty people. Second line contains $ n $ space-separated integers $ L_{1},L_{2},...,L_{n} $ ( $ 0<=L_{i}<=10^{9} $ ), where $ L_{i} $ is the length of the $ i $ -th person's claw.

Print one integer — the total number of alive people after the bell rings.

4
0 1 0 10

1

2
0 0

2

10
1 1 3 0 0 0 2 1 0 3

3

In first sample the last person kills everyone in front of him.