#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, k;
    cin >> n >> k;

    vector<int64_t> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    sort(a.begin(), a.end());

    if (k == 1) {
        cout << a[n - 1] - a[0] << endl;
        quick_exit(0);
    }

    vector<int64_t> b(n - 1);
    for (int i = 0; i < n - 1; i++) {
        b[i] = a[i + 1] - a[i];
    }

    sort(b.begin(), b.end());
    int64_t r = 0;
    for (int i = 0; i < k - 1; i++) {
        r += b[n - 2 - i];
    }

    cout << a[n - 1] - a[0] - r << endl;

    return 0;
}