#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long
const int INF = 1LL << 60;

signed main(){

  int n, k; cin >> n >> k;
  vector<int> a(n);
  for(int i = 0; i < n; i++){
    cin >> a[i];
  }

  sort(a.begin(),a.end());
  vector<int> v;
  for(int i = 0; i < n-1; i++){
    v.push_back(a[i+1] - a[i]);
  }
  sort(v.begin(),v.end());

  int ans = 0;
  for(int i = 0; i < n-1 - (k-1); i++){
    ans += v[i];
  }
  cout << ans << endl;

  return 0;
}