#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  ll n,k;
  cin>>n>>k;
  vector<ll> A(n);
  rep(i,n) cin>>A[i];
  sort(ALL(A));
  reverse(ALL(A));
  vector<ll> B(n-1);
  rep(i,n-1) B[i]=A[i]-A[i+1];
  sort(ALL(B));
  reverse(ALL(B));
  ll sum=0;
  rep(i,k-1) sum+=B[i];
  cout<<A[0]-A[n-1]-sum<<endl;
  
  return 0;
}