#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint MOD = 1e12;

signed main(){
  lint n, K; cin >> n >> K;
  vector<lint> a(n);
  for(int i = 0; i < n; i++) cin >> a[i];
  sort(a.begin(), a.end());
  vector<lint> b;
  for(int i = 1; i < n; i++) b.push_back(a[i] - a[i - 1]);
  sort(b.begin(), b.end());
  lint ans = 0;
  for(int i = 0; i < n - K; i++) ans += b[i];
  cout << ans << endl;
}