#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <queue>
using ll = long long;
using namespace std;
ll a[50100];
vector<ll> v;
int main(void)
{
    int N, K;
    cin >> N >> K;
    for (int i = 0; i < N; ++i)
        cin >> a[i];

    sort(a, a + N);

    for (int i = 1; i < N; ++i)
    {
        v.push_back(a[i] - a[i - 1]);
    }

    ll ans = 0;
    sort(v.begin(), v.end());

    for (int i = 0; i < N - K; ++i)
        ans += v[i];

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