#include <bits/stdc++.h>

#define VARNAME(x) #x
#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;
using ld = long double;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz:" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = (ll)1e9 + 7LL;
constexpr ld PI = static_cast<ld>(3.1415926535898);

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 10;


int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, K;
    cin >> N >> K;
    vector<ll> a(N);
    vector<ll> sa(N - 1);
    for (int i = 0; i < N; i++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    ll ans = a.back() - a.front();
    for (int i = 0; i < N - 1; i++) {
        sa[i] = a[i + 1] - a[i];
    }
    sort(sa.begin(), sa.end(), greater<ll>{});
    ll sum = 0;
    for (int i = 0; i < K - 1; i++) {
        sum += sa[i];
    }
    cout << ans - sum << endl;

    return 0;
}