#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define show(x) cout<<#x<<"="<<x<<"\n"
using namespace std;

int n,m;
string s;
ll a[50001];
ll b[50001];

int main(){
 ios::sync_with_stdio(false);
 cin.tie(0);
 cout.precision(10);
 cout<<fixed;
#ifdef LOCAL_DEFINE
  FILE *stream1;
  //FILE *stream2;
  stream1=freopen("in", "r", stdin); 
  //stream2=freopen("out","w",stdout);
  if(stream1==NULL)return 0;
  //if(stream2==NULL)return 0;
#endif
 cin>>n>>m;
 for(int i=0;i<n;i++){
  cin>>a[i];
 }
 sort(a,a+n);
 vector<pair<ll,int> > v;
 for(int i=1;i<n;i++){
  v.push_back(make_pair(a[i]-a[i-1],i));
 }
 sort(v.begin(),v.end());
 reverse(v.begin(),v.end());
 for(int i=0;i<m-1;i++){
  b[i]=v[i].se;
 }
 sort(b,b+m-1);
 ll ans=0;
 int pre=0;
 for(int i=0;i<m-1;i++){
  ans+=abs(a[pre]-a[b[i]-1]);
  pre=b[i];
 }
 ans+=abs(a[pre]-a[n-1]);
 cout<<ans<<"\n";
#ifdef LOCAL_DEFINE
  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
  fclose(stream1);
  //fclose(stream2);
#endif
 return 0;
}