#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <numeric>
#include <cstring>
#include <cmath>
#include <set>
#include <queue>
#include <stack>

const int MOD = 1e9 + 7;
const int iINF = 100000000;
#define rep(i, n) for (int i = 0; i < (n); i++)

using namespace std;
using ll = long long int;
using P = pair<int, int>;
using edge = struct
{
    int to;
    int cost;
};

int main()
{
    int N, K;
    ll a[50010];
    ll dist[10010];
    cin >> N >> K;
    rep(i, N) cin >> a[i];
    sort(a, a + N);

    for (int i = 0; i < N - 1; i++)
        dist[i] = a[i + 1] - a[i];

    ll sum = 0LL;

    sort(dist, dist + N - 1);

    for (int i = 0; i < N - K; i++)
        sum += dist[i];

    cout << sum << endl;

    return 0;
}