#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;

int main(){
  int n, k;
  cin >> n >> k;
  vector<ll> a(n);
  rep(i,n) cin >> a[i];
  sort(a.begin(), a.end());
  vector<ll> dif(n-1);
  ll res = 0;
  rep(i,n-1){
    dif[i] = a[i+1] - a[i];
    res += dif[i];
  }
  sort(dif.begin(), dif.end(), greater<ll>());
  rep(i,k-1){
    res -= dif[i];
  }
  cout << res << endl;
  return 0;
}