#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i,a) for(int i=0;i<(a);i++)
#define MOD 1000000007

int main(){
  int N,K; cin>>N>>K;
  ll a[N];
  rep(i,N) cin>>a[i];
  sort(a,a+N);
  vector<pair<ll,int>> dif(N-1);
  rep(i,N-1) dif[i]={a[i+1]-a[i],i};
  sort(dif.rbegin(),dif.rend());
  ll ans=0, mi=a[0];
  rep(i,K-1){
    int ind=dif[i].second;
    ans+=a[ind]-mi;
    mi=a[ind+1];
  }
  ans+=a[N-1]-mi;
  cout<<ans<<endl;
  return 0;
}