#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
using namespace std;
#define OVERLOAD_REP(_1, _2, _3, name, ...) name
#define REP1(i, n) for (auto i = std::decay_t<decltype(n)>{}; (i) != (n); ++(i))
#define REP2(i, l, r) for (auto i = (l); (i) != (r); ++(i))
#define rep(...) OVERLOAD_REP(__VA_ARGS__, REP2, REP1)(__VA_ARGS__)
#define REP(i, l, r) rep(i, l, r+1)
#define all(x) (x).begin(),(x).end()
#define inf 1000000000
using ll = long long;
using P = pair<int,int>;
using Graph = vector<vector<int> >;

int main() {
    // 高速化
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // 小数点の出力桁数を指定
    cout << fixed << setprecision(10);

    // メイン
    int N, K;
    cin >> N >> K;
    vector<ll> a(N);
    rep(i, 0, N) cin >> a[i];
    sort(all(a));
    vector<pair<ll, int> > sa(N-1);
    rep(i, 0, N-1) sa[i] = {a[i+1]-a[i], i+1};
    sort(sa.rbegin(), sa.rend());
    vector<int> wake;
    wake.push_back(0);
    rep(i, 0, K-1) wake.push_back(sa[i].second);
    wake.push_back(N);
    sort(all(wake));

    //rep(i, 0, N) cout << a[i] << " ";
    //cout << endl;
    //rep(i, 0, K+1) cout << wake[i] << " ";
    //cout << endl;

    ll ans = 0;
    rep(i, 0, K) {
        ans += a[wake[i+1]-1] - a[wake[i]];
    }
    cout << ans << endl;

    return 0;
}