//#include <atcoder/all>
#include <iostream>
#include <numeric>
#include <cmath>
#include <limits>
#include <stdio.h>
#include <iomanip>
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <unordered_set> // unordered_set
#include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower
using namespace std;
//using namespace atcoder;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<ll>>;

int main() {
	ll N, K;
	cin >> N >> K;
	vll A(N);
	rep(i, N)cin >> A[i];
	sort(all(A));


	ll S = 0;
	vll B(N - 1);
	rep(i, N - 1) {
		B[i] = -A[i] + A[i + 1];
		S += B[i];

	}
	sort(all(B));
	reverse(all(B));
	rep(i,K-1) {
		S -= B[i];
	}
	cout << S << endl;

}