#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <math.h>

using ll = long long;
using namespace std;

const int MOD = 1e9+7;

int main() {
    int N, K;
    cin >> N >> K;
    vector<ll> a(N), b(N-1);
    for(int i = 0; i < N; i++)
    {
        cin >> a[i];
    }
    sort(a.begin(),a.end());
    for(int i = 0; i < N-1; i++)
    {
        b[i] = a[i+1] - a[i];
    }
    sort(b.begin(),b.end());
    ll ans = 0;
    for(int i = 0; i < N-K; i++)
    {
        ans += b[i];
    }
    cout << ans << endl;
    return 0;
}