#include <bits/stdc++.h>
using namespace std;

int main() {

	int N; cin >> N;
	int K; cin >> K;
	long long int  a[50004];
	for (int i = 0; i < N; i++) {
		cin >> a[i];
	}
	long long ans = 0;
	sort(a, a + N);

	ans = a[N - 1] - a[0];
	long long int b[50004];
	for (int i = 0; i < N - 1; i++) {
		b[i] = a[i + 1] - a[i];
	}
	sort(b, b + N - 1);
	/*for (int i = 0; i < N - 1; i++) {
		cout << b[i] << " ";
	}cout << endl;*/
	long long sum = 0;
	for (int k = 0; k < K - 1; k++) {
		sum += b[N - 2 - k];
	}
	//cout << "ans :" << ans << endl;
	//cout << "sum :" << sum << endl;
	cout << ans - sum << endl;


	return 0;
}