#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n, k;
    cin >> n >> k;
    ll a[n];
    rep(i,n)cin >> a[i];
    sort(a,a+n);
    ll b[n-1];
    rep(i,n-1)b[i] = a[i+1] - a[i];
    sort(b,b+n-1);

    ll ans = 0;
    rep(i,n-k){
        ans += b[i];
    }

    cout << ans << endl;
    return 0;
}