### BUGGY CODE ###

import math, string, itertools, fractions, heapq, collections, re,  array, bisect, sys, random, time, copy, functools
#  import numpy as np

sys.setrecursionlimit(10**7)
inf = 10 ** 20
eps = 1.0 / 10**10
mod = 10**9+7
dd = [(-1, 0), (0, 1), (1, 0), (0, -1)]
ddn = [(-1, 0), (-1, 1), (0, 1), (1, 1), (1, 0), (1, -1), (0, -1), (-1, -1)]


def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)


def main():
    N, K = LI()
    T = []
    D = []
    TD = []
    [TD.append(LI()) for i in range(N)]
    # sort desc
    #  TD = np.array(TD)
    #  TD = TD[np.argsort(TD[:, 1])[::-1]]
    TD = sorted(TD, key=lambda l:l[1], reverse=True)
    #  print(TD)

    #  print(TD)
    # 種類のカウントをもつ
    type_count_dict = {}
    for i in TD:
        if not type_count_dict.get(i[0]):
            type_count_dict[i[0]] = 0
    #  print(type_count_dict)

    S = TD[:K]
    #  print('S', S)
    for i in S:
        type_count_dict[i[0]] += 1

    #  print('type_count', type_count_dict)
    base_point = sum(i[1] for i in S)
    type_bonus = len(set([i[0] for i in S]))
    result = base_point + type_bonus**2
    results = [result]
    #  print('base_point, type_bonus, result', base_point, type_bonus**2, result)

    remaining_items = []
    done_types = []
    #  print('type_count_dict', type_count_dict)
    for i in TD[K:]:
        if i[0] in done_types:
            continue
        if type_count_dict[i[0]] == 0:
            remaining_items.append(i[1])
            done_types.append(i[0])
    #  print('remaining_items', remaining_items)

    ridx = 0
    for idx, s in enumerate(S[::-1]):
        if len(remaining_items) < ridx + 1:
            break
        if len(remaining_items) == 0:
            break
        if type_count_dict[s[0]] >= 2:
            # print('s', s)
            type_count_dict[s[0]] -= 1
            base_point += remaining_items[ridx] - s[1]
            type_bonus += 1
            ridx += 1
            results.append(type_bonus**2 + base_point)

    print(max(results))


if __name__ == '__main__':
    main()


### FIXED CODE ###

#  import math, string, itertools, fractions, heapq, collections, re,  array, bisect, sys, random, time, copy, functools
import sys
#  import numpy as np
#  from queue import PriorityQueue

sys.setrecursionlimit(10**7)
inf = 10 ** 20
eps = 1.0 / 10**10
mod = 10**9+7
dd = [(-1, 0), (0, 1), (1, 0), (0, -1)]
ddn = [(-1, 0), (-1, 1), (0, 1), (1, 1), (1, 0), (1, -1), (0, -1), (-1, -1)]


def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)


def main():
    N, K = LI()
    T = []
    D = []
    TD = []
    [TD.append(LI()) for i in range(N)]
    # sort desc
    #  TD = np.array(TD)
    #  TD = TD[np.argsort(TD[:, 1])[::-1]]
    TD = sorted(TD, key=lambda l:l[1], reverse=True)
    #  print(TD)

    #  print(TD)
    # 種類のカウントをもつ
    type_count_dict = {}
    base_point = 0
    type_bonus = 0
    remaining_items = []
    for idx, i in enumerate(TD):
        if not type_count_dict.get(i[0]):
            type_count_dict[i[0]] = 0
        if idx < K:
            if type_count_dict[i[0]] == 0:
                type_bonus += 1
            type_count_dict[i[0]] += 1
            base_point += i[1]
        else:
            if type_count_dict[i[0]] == 0:
                remaining_items.append(i[1])
                type_count_dict[i[0]] += 1

    #  print(type_count_dict)

    S = TD[:K]
    #  print('S', S)
    #  for i in S:
    #      type_count_dict[i[0]] += 1
    #      base_point += i[1]

    #  print('type_count', type_count_dict)
    #  base_point = sum(i[1] for i in S)
    #  type_bonus = len(set([i[0] for i in S]))
    result = base_point + type_bonus**2
    #  results = [result]
    #  print('base_point, type_bonus, result', base_point, type_bonus**2, result)

    #  remaining_items = []
    #  remaining_items = PriorityQueue()
    #  done_types = []
    #  print('type_count_dict', type_count_dict)
    #  for i in TD[K:]:
    #      if i[0] in done_types:
    #          continue
    #      if type_count_dict[i[0]] == 0:
    #          remaining_items.append(i[1])
    #          #  remaining_items.put((-i[1], i[1]))
    #          done_types.append(i[0])
    #  print('remaining_items', remaining_items)

    ridx = 0
    for idx, s in enumerate(S[::-1]):
        if len(remaining_items) < ridx + 1:
            break
        if len(remaining_items) == 0:
            break
        #  if remaining_items.empty():
        #      break
        if type_count_dict[s[0]] >= 2:
            # print('s', s)
            type_count_dict[s[0]] -= 1
            base_point += remaining_items[ridx] - s[1]
            #  base_point += remaining_items.get()[1] - s[1]
            type_bonus += 1
            ridx += 1
            #  results.append(type_bonus**2 + base_point)
            result = max(type_bonus**2 + base_point, result)

    #  print(max(results))
    print(result)


if __name__ == '__main__':
    main()