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

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, k;
	cin >> n >> k;
	vector<ll> a(n);
	rep(i, n) cin >> a[i];

	sort(all(a));

	vector<ll> b(n - 1);
	rep(i, n - 1) {
		b[i] = a[i + 1] - a[i];
	}

	sort(all(b));
	ll ans = 0;
	rep(i, n - k) ans += b[i];

	dunk(ans);

	return 0;
}