#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
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());
  priority_queue<Int,vector<Int>,greater<Int> > pq;
  for(Int i=1;i<n;i++) pq.emplace(a[i]-a[i-1]);
  Int ans=0;
  for(Int i=k;i<n;i++){
    ans+=pq.top();pq.pop();
  }
  cout<<ans<<endl;
  return 0;
}