#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

void solve() {
    int N, K;
    cin >> N >> K;
    vll a(N);
    rep(i, N) {
        cin >> a[i];
    }
    sort(all(a));
    vll d(N - 1);
    rep(i, N - 1) {
        d[i] = a[i + 1] - a[i];
    }

    sort(rbegin(d), rend(d));
    ll ans = a[N - 1] - a[0];
    rep(i, K - 1) {
        ans -= d[i];
    }
    cout << ans << endl;

}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}