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

int main(){
    int N,K;
    long int in, ans=0;
    vector<long int> v, diff;


    cin >> N >> K;
    while(cin >> in) v.push_back(in);
    sort(v.begin(),v.end());

    for(int i=0;i<N-1;i++) diff.push_back(v[i+1]-v[i]);
    sort(diff.begin(),diff.end());
    for(int i=0;i<N-K;i++) ans+=diff[i];

    cout << ans << endl;

    return 0;
}