#include<bits/stdc++.h>
using namespace std;
long long a[99999], ans = 0;
int main(){
	int n, k;
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	sort(a + 1, a + n + 1);
	for (int i = 1; i < n; i++)
		a[i] = a[i + 1] - a[i];
	sort(a + 1, a + n);
	for (int i = 1; i <= n - k; i++)
		ans += a[i];
	cout << ans << endl;
	return 0;
}