#include<bits/stdc++.h>
using namespace std;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, K;
    cin >> N >> K;
    vector<long long> As(N, 0LL);
    for (auto & a : As) cin >> a;
    sort(As.begin(), As.end());
    long long total = As[N - 1] - As[0];
    if (K == 1){
        cout << total << endl;
        return 0;
    }
    vector<long long> Bs(N - 1, 0LL);
    for (int i = 0; i < N - 1; ++i) Bs[i] = As[i + 1] - As[i];
    sort(Bs.begin(), Bs.end());
    for (auto it = Bs.rbegin(); it != Bs.rbegin() + (K - 1); ++it){
        total -= *it;
    }
    cout << total << endl;
    return 0;
}