1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
#include <bits/stdc++.h>

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define debug std::cout << "hmm" << std::endl;
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::pair<ll, ll> pll;
typedef std::vector<int> vi;
typedef std::vector<ll> vl;

template <typename T>
void print(T t)
{
    std::cout << t << ' ';
}
template <typename T1, typename T2>
void print(std::pair<T1, T2> t)
{
    std::cout << '{' << t.first << ' ' << t.second << '}';
}
template <typename T>
void print(std::vector<T> t)
{
    for (auto a : t)
        print(a);
    std::cout << std::endl;
}

main()
{
    std::cin.tie(0)->sync_with_stdio(0);
    std::cin.exceptions(std::cin.failbit);

    int Z = 1;
    //std::cin >> Z;
    while (Z--)
    {
        ll n, k;
        std::cin >> n >> k;
        vi V(n);
        for (auto &a : V)
            std::cin >> a;
        vl F(n, -1);
        for (int i = 0; i < n; i++)
            if (F[V[i] - 1] < 0)
                F[V[i] - 1] = i;
        std::sort(all(F));
        std::reverse(all(F));
        while (F.size() && F.back() < 0)
            F.resize(F.size() - 1);
        if (F.size() < k)
        {
            std::cout << -1;
            continue;
        }
        std::reverse(all(F));
        ll W = 0;
        for (int i = 0; i < k; i++)
            W += F[i];
        W -= (k * (k - 1)) / 2;
        std::cout << W;
    }
}