class Bit:
    def __init__(self, n):
        self.size = n
        self.tree = [0] * (n + 1)
    
    def range_sum(self, l, r):
        return self.sum(r - 1) - self.sum(l - 1)
        
        
    def sum(self, i):
        i += 1
        s = 0
        while i > 0:
            s += self.tree[i]
            i -= i & -i
        return s
        
    def get(self, i):
        return self.sum(i) - self.sum(i - 1)
 
    def add(self, i, x):
        i += 1
        while i <= self.size:
            self.tree[i] += x
            i += i & -i

m, k = map(int, input().split())
A = list(map(int, input().split()))

ans = [0] * m
cnt = [0] * m
lst = []
for a in A:
    c = cnt[a] * m + a
    lst.append(c)
    cnt[a] += 1
bit = Bit(m * k)
ans_base = 0
for a in lst:
    ans_base += bit.range_sum(a, m * k)
    bit.add(a, 1)

cnt = [0] * m
for i in range(k):
    lst = []
    for j in range(i * m, i * m + m):
        a = A[j]
        c = cnt[a] * m + a
        lst.append(c)
        cnt[a] += 1
    dic = {l:i for i, l in enumerate(sorted(lst))}
    bit = Bit(m)
    tot = 0
    for a in lst:
        a = dic[a]
        tot += bit.range_sum(a, m)
        bit.add(a, 1)
    base = tot
    i = 1
    for a in lst[:-1]:
        a = dic[a]
        tot -= a
        tot += m - a - 1
        ans[i] += tot - base
        i += 1

print(min(ans) + ans_base)