CF34B.Sale

Once Bob got to a sale of old TV sets. There were n TV sets at that sale. TV set with index i costs a__i bellars. Some TV sets have a negative price — their owners are ready to pay Bob if he buys their useless apparatus. Bob can «buy» any TV sets he wants. Though he's very strong, Bob can carry at most m TV sets, and he has no desire to go to the sale for the second time. Please, help Bob find out the maximum sum of money that he can earn.

有一次，Bob 去参加了一场旧电视机的促销活动。这场促销活动共有 $n$ 台电视机。编号为 $i$ 的电视机售价为 $a_i$ 贝拉尔（bellars）。某些电视机的价格为负数——这意味着它们的主人愿意付钱给 Bob，只要他买下这些无用的设备。Bob 可以“购买”任意数量的电视机。尽管他非常强壮，但他最多只能携带 $m$ 台电视机，并且他不想第二次前往这场促销活动。请帮助 Bob 计算他最多能赚多少钱。

The first line contains two space-separated integers n and m (1 ≤ m ≤ n ≤ 100) — amount of TV sets at the sale, and amount of TV sets that Bob can carry. The following line contains n space-separated integers a__i ( - 1000 ≤ a__i ≤ 1000) — prices of the TV sets.

第一行包含两个以空格分隔的整数 $n$ 和 $m$（$1 \le m \le n \le 100$）—— 促销中电视的数量，以及 Bob 能携带的电视数量。
接下来的一行包含 $n$ 个以空格分隔的整数 $a_i$（$-1000 \le a_i \le 1000$）—— 各台电视的价格。

Output the only number — the maximum sum of money that Bob can earn, given that he can carry at most m TV sets.

输出唯一的一个数字——鲍勃最多能赚取的钱数，已知他最多能携带 m 台电视机。