#include "bits/stdc++.h"
#define REP(i,n,N) for(ll i=(n); i<(N); i++)
#define RREP(i,n,N) for(int i=(N-1); i>=n; i--)
#define CK(n,a,b) (a)<=(n)&&(n)<(b)
#define ALL(v) (v).begin(),(v).end()
#define p(s) cout<<(s)<<endl
typedef long long ll;
using namespace std;
const ll inf=1e18;

ll N, K;
int main(){
    while(cin>>N>>K){
        ll a[50100];
        REP(i,0,N){
            cin>>a[i];
        }
        sort(a,a+N);
        priority_queue<ll> pq;
        REP(i,0,N-1){
            pq.push(a[i+1]-a[i]);
        }
        ll ans=a[N-1]-a[0];
        REP(i,0,K-1){
            ans-=pq.top();
            pq.pop();
        }
        p(ans);
    }
    return 0;
}