#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
using ll = long long;

int main() {
    int n, k;
    cin >> n >> k;
    vector<ll> a(n);
    for (int i = 0; i < n; i++)cin >> a[i];
    sort(a.begin(), a.end());

    vector<ll> b(n - 1);
    for (int i = 0; i < n - 1; i++)b[i] = a[i + 1] - a[i];
    sort(b.begin(), b.end(), greater<>());

    ll ret = a.back() - a.front();
    for (int i = 0; i < k - 1; i++)ret -= b[i];
    cout << ret << endl;
    return 0;
}