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

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

    int N, K; cin >> N >> K;
    vector<ll> a(N);
    rep(i, N) cin >> a[i];
    sort(a.begin(), a.end());

    vector<ll> d(N - 1);
    rep(i, N - 1) d[i] = a[i + 1] - a[i];
    sort(d.begin(), d.end());
    ll ans = 0;
    rep(i, N - K) ans += d[i];
    cout << ans << endl;
}