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

#define all(v) v.begin(),v.end()
using ll = long long;
const ll INF=1ll<<60;
using vll = vector<ll> ;

int main(){
    ll N,K;
    cin>>N>>K;
    vll A(N);
    for(auto &e:A) cin >>e;
    ll ans=0;
    sort(all(A));
    ans+=A[N-1]-A[0];
    vll s;
    for(int i=0;i<N-1;i++){
        s.push_back(A[i+1]-A[i]);
    }
    sort(all(s));reverse(all(s));
    for(int i=0;i<K-1;i++){
        ans-=s[i];
    }
    cout << ans << endl;
}