#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int N, K;
    cin >> N >> K;
    vector<ll> A(N);
    rep(i, 0, N) cin >> A[i];
    sort(all(A));
    vector<ll> D(N - 1);
    rep(i, 0, N - 1) D[i] = A[i + 1] - A[i];
    
    sort(D.rbegin(), D.rend());
    
    ll sum = 0;
    rep(i, 0, K - 1) sum += D[i];
    cout << A[N - 1] - A[0] - sum << '\n';
}