# -*- coding: utf-8 -*-

"""
参考：https://img.atcoder.jp/abc116/editorial.pdf
"""

import sys, re
from collections import deque, defaultdict, Counter
from math import sqrt, hypot, factorial, pi, sin, cos, radians
from heapq import heappop, heappush, heapify, heappushpop
from bisect import bisect_left, bisect_right
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from functools import reduce, partial
from fractions import Fraction
from string import ascii_lowercase, ascii_uppercase, digits

def input(): return sys.stdin.readline().strip()
def ceil(a, b=1): return int(-(-a // b))
def round(x): return int((x*2+1) // 2)
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N, K = MAP()
tdN = [[0]*2 for i in range(N)]
for i in range(N):
    t, d = MAP()
    tdN[i][0] = t
    tdN[i][1] = d

tdN.sort(key=itemgetter(1),reverse=True)
base = 0
bonus = 0
c = Counter()
changes = []
ans = 0
for i in range(K):
    t, d = tdN[i]
    base += d
    if c[t] == 0:
        bonus += 1
    c[t] += 1
    if c[t] >= 2:
        heappush(changes, (d, i))
bonus *= bonus
ans = base + bonus

for i in range(K, N):
    t, d = tdN[i]
    # 既に持ってるネタならスキップ
    if c[t] != 0:
        continue
    else:
        # 1つずつ候補から交換してみて、最大値を取る
        _, idx = heappop(changes)
        t2, d2 = tdN[idx]
        base -= d2 - d
        bonus = (sqrt(bonus)+1) ** 2
        ans = max(base + bonus, ans)
print(int(ans))


### FIXED CODE ###

# -*- coding: utf-8 -*-

"""
参考：https://img.atcoder.jp/abc116/editorial.pdf
"""

import sys, re
from collections import deque, defaultdict, Counter
from math import sqrt, hypot, factorial, pi, sin, cos, radians
from heapq import heappop, heappush, heapify, heappushpop
from bisect import bisect_left, bisect_right
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from functools import reduce, partial
from fractions import Fraction
from string import ascii_lowercase, ascii_uppercase, digits

def input(): return sys.stdin.readline().strip()
def ceil(a, b=1): return int(-(-a // b))
def round(x): return int((x*2+1) // 2)
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N, K = MAP()
tdN = [[0]*2 for i in range(N)]
for i in range(N):
    t, d = MAP()
    tdN[i][0] = t
    tdN[i][1] = d

tdN.sort(key=itemgetter(1),reverse=True)
base = 0
bonus = 0
c = Counter()
changes = []
ans = 0
for i in range(K):
    t, d = tdN[i]
    base += d
    if c[t] == 0:
        bonus += 1
    c[t] += 1
    # 交換候補を集める
    if c[t] >= 2:
        heappush(changes, (d, i))
bonus *= bonus
ans = base + bonus

for i in range(K, N):
    t, d = tdN[i]
    # 既に持ってるネタならスキップ
    if c[t] != 0:
        continue
    else:
        # 1つずつ候補から交換してみて、最大値を取る
        if len(changes):
            _, idx = heappop(changes)
            t2, d2 = tdN[idx]
            base -= d2 - d
            bonus = (sqrt(bonus)+1) ** 2
            ans = max(base + bonus, ans)
            # 今回交換した分を更新
            c[t2] -= 1
            c[t] += 1
print(int(ans))