CF1082C.Multi-Subject Competition

A multi-subject competition is coming! The competition has $m$ different subjects participants can choose from. That's why Alex (the coach) should form a competition delegation among his students.

He has $n$ candidates. For the $i$-th person he knows subject $s_i$ the candidate specializes in and $r_i$ — a skill level in his specialization (this level can be negative!).

The rules of the competition require each delegation to choose some subset of subjects they will participate in. The only restriction is that the number of students from the team participating in each of the chosen subjects should be the same.

Alex decided that each candidate would participate only in the subject he specializes in. Now Alex wonders whom he has to choose to maximize the total sum of skill levels of all delegates, or just skip the competition this year if every valid non-empty delegation has negative sum.

(Of course, Alex doesn't have any spare money so each delegate he chooses must participate in the competition).

多学科竞赛即将开始！本次竞赛共有 $m$ 个不同学科供参赛者选择。因此，Alex（教练）需要从他的学生中组建一支竞赛代表队。

他有 $n$ 名候选人。对于第 $i$ 名候选人，Alex 知道其专长学科 $s_i$ 以及在该学科上的技能水平 $r_i$（该水平可能为负数！）。

竞赛规则要求每支代表队必须选择一个学科子集参与比赛。唯一限制是：所选的每个学科中，代表队派出的学生人数必须相同。

Alex 决定每位候选人仅能参加其专长学科的比赛。现在 Alex 想知道：应选择哪些候选人，才能使所有代表队员的技能水平总和最大化；或者，若每个合法的非空代表队的技能水平总和均为负数，则干脆放弃今年的比赛。

（当然，Alex 没有多余经费，因此他选出的每位代表队员都必须实际参赛。）

The first line contains two integers $n$ and $m$ ($1 \le n \le 10^5$, $1 \le m \le 10^5$) — the number of candidates and the number of subjects.

The next $n$ lines contains two integers per line: $s_i$ and $r_i$ ($1 \le s_i \le m$, $-10^4 \le r_i \le 10^4$) — the subject of specialization and the skill level of the $i$-th candidate.

第一行包含两个整数 $n$ 和 $m$（$1 \le n \le 10^5$，$1 \le m \le 10^5$）—— 分别表示候选人的数量和科目的数量。

接下来的 $n$ 行每行包含两个整数：$s_i$ 和 $r_i$（$1 \le s_i \le m$，$-10^4 \le r_i \le 10^4$）—— 分别表示第 $i$ 位候选人的专长科目和技能水平。

Print the single integer — the maximum total sum of skills of delegates who form a valid delegation (according to rules above) or $0$ if every valid non-empty delegation has negative sum.

输出一个整数——即组成合法代表团（依据上述规则）的代表们的技能总和的最大值；如果每个合法的非空代表团的技能总和均为负数，则输出 $0$。

In the first example it's optimal to choose candidates $1$, $2$, $3$, $4$, so two of them specialize in the $2$-nd subject and other two in the $3$-rd. The total sum is $6 + 6 + 5 + 5 = 22$.

In the second example it's optimal to choose candidates $1$, $2$ and $5$. One person in each subject and the total sum is $6 + 6 + 11 = 23$.

In the third example it's impossible to obtain a non-negative sum.

在第一个例子中，最优方案是选择候选人 $1$、$2$、$3$、$4$，其中两人专攻第 $2$ 门科目，另外两人专攻第 $3$ 门科目。总分为 $6 + 6 + 5 + 5 = 22$。

在第二个例子中，最优方案是选择候选人 $1$、$2$ 和 $5$，每门科目各一人，总分为 $6 + 6 + 11 = 23$。

在第三个例子中，无法得到非负的总分。