#include <iostream>
#include <iomanip>
#include <cstring>
#include <algorithm> 
#include <math.h>
#include <queue>
#include <functional>
#include <map>
#include <vector>
#include <string>
using namespace std;
typedef long long ll;
const ll MOD = 1000000007;

int n, k;
ll a[100005],b[100005];
ll ans;
int main(void){
    cin >> n >> k;
    ans = 0;
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    for (int i = 0; i < n - 1; i++){
        b[i] = a[i + 1] - a[i];
        ans += b[i];
    }
    sort(b, b + n - 1);
    for (int i = n - 2; i >= n - k; i--){
        ans -= b[i];
    }

    cout << ans << endl;


}