#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define llong long long

int main() {
    int n, k;
    cin >> n >> k;
    vector<llong> a(n);
    rep(i, n) cin >> a[i];

    sort(a.begin(), a.end());
    if(k == 1) {
        cout << a[n-1] - a[0] << "\n";
    } else {
        priority_queue<llong> borders;
        rep(i, n-1) {
            borders.push(a[i+1] - a[i]);
        }
        llong result = a[n-1] - a[0];
        rep(i, k-1) {
            result -= borders.top();
            borders.pop();
        }
        cout << result << "\n";
    }
}