#include <bits/stdc++.h>
typedef  long long ll;
#define INF 1000000000
using namespace std;
#define N 1000000
#define MOD 1000000007
int main(void){
    ll n,k;
    cin>>n>>k;
    vector<ll>a(n);
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    sort(a.begin(),a.end());
    vector<ll>diff(n-1);
    for(int i=0;i<n-1;i++){
        diff[i]=a[i+1]-a[i];
    }
    sort(diff.begin(),diff.end());
    ll ans=0;
    for(int i=0;i<n-k;i++){
        ans+=diff[i];
    }
    cout<<ans<<endl;
}