Microtransactions (easy version)

有 $n$ 种物品，对于第 $i$ $(1\le i \le n)$ 个物品，你需要买 $k_i$ 个（你每次购物是在**晚上**），每个物品在非打折日买是 $2$ 块钱，在打折日买是 $1$ 块钱，每天**早上**你可以赚 $1$ 块钱，一共有 $m$ 个打折日，在第 $d_i$ 天第 $t_i$ 种物品打折，问最少需要多少天可以买完你需要的物品。注意，你每天可以买任意多数量以及种类的商品（只要你有足够的余额）。 ### 输入格式 第一行包含两个整数 $n$ 和 $m$ $(1\le n,m \le 1000)$ 中的商品类型数和打折的天数。 输入的第二行包含 $n$ 个整数 $k_i$，其中 $k_i$ 是第 $i$ 类需要的个数。$(0 \le \sum k_i \le 1000)$。 接下来的 $m$ 行，每行两个数 $(d_i,t_i$) $(1 \le d_i \le 1000, 1 \le t_i \le n)$，表示第 $t_i$ 个商品在 $d_i$ 天打特价。 ### 输出格式 一个整数，表示最早在哪一天能买完所有需要的商品。

The only difference between easy and hard versions is constraints. Ivan plays a computer game that contains some microtransactions to make characters look cooler. Since Ivan wants his character to be really cool, he wants to use some of these microtransactions — and he won't start playing until he gets all of them. Each day (during the morning) Ivan earns exactly one burle. There are $ n $ types of microtransactions in the game. Each microtransaction costs $ 2 $ burles usually and $ 1 $ burle if it is on sale. Ivan has to order exactly $ k_i $ microtransactions of the $ i $ -th type (he orders microtransactions during the evening). Ivan can order any (possibly zero) number of microtransactions of any types during any day (of course, if he has enough money to do it). If the microtransaction he wants to order is on sale then he can buy it for $ 1 $ burle and otherwise he can buy it for $ 2 $ burles. There are also $ m $ special offers in the game shop. The $ j $ -th offer $ (d_j, t_j) $ means that microtransactions of the $ t_j $ -th type are on sale during the $ d_j $ -th day. Ivan wants to order all microtransactions as soon as possible. Your task is to calculate the minimum day when he can buy all microtransactions he want and actually start playing.

The first line of the input contains two integers $ n $ and $ m $ ( $ 1 \le n, m \le 1000 $ ) — the number of types of microtransactions and the number of special offers in the game shop. The second line of the input contains $ n $ integers $ k_1, k_2, \dots, k_n $ ( $ 0 \le k_i \le 1000 $ ), where $ k_i $ is the number of copies of microtransaction of the $ i $ -th type Ivan has to order. It is guaranteed that sum of all $ k_i $ is not less than $ 1 $ and not greater than $ 1000 $ . The next $ m $ lines contain special offers. The $ j $ -th of these lines contains the $ j $ -th special offer. It is given as a pair of integers $ (d_j, t_j) $ ( $ 1 \le d_j \le 1000, 1 \le t_j \le n $ ) and means that microtransactions of the $ t_j $ -th type are on sale during the $ d_j $ -th day.

Print one integer — the minimum day when Ivan can order all microtransactions he wants and actually start playing.

5 6
1 2 0 2 0
2 4
3 3
1 5
1 2
1 5
2 3

8

5 3
4 2 1 3 2
3 5
4 2
2 5

20