#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <set>
#include <map>
#include <numeric>
#include <regex>
#include <tuple>
#include<iomanip>
using namespace std;

typedef long long ll;
typedef pair<int, int> P;
#define MOD 1000000007 // 10^9 + 7
#define INF 1000000000 // 10^9
#define LLINF 1LL<<60

ll a[50009];
ll b[50009];

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

	int N, K; cin >> N >> K;
	ll Sum = 0LL;
	for (int i = 0; i < N; i++) {
		cin >> a[i];
	}
	sort(a, a + N);

	for (int i = 0; i < N - 1; i++) b[i] = (a[i + 1] - a[i]);
	sort(b, b + N - 1, greater<ll>());

	for (int i = 0; i < N - 1; i++) Sum += b[i];

	for (int i = 0; i < K - 1; i++) Sum -= b[i];


	cout << Sum << endl;


	return 0;
}