#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <functional>

#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define MOD 1000000007
#define int long long
using ll = long long;
using namespace std;
const int INF = 1LL << 50;
using P = pair<int, int>;

template <class T>
bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
template <class T>
bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
struct Setup {
    Setup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} SETUP;

signed main() {
    int n, k; cin >> n >> k;
    vector<int> as(n);
    for (auto&a : as) {
        cin >> a;
    }
    sort(as.begin(), as.end());

    // 差の集合をソートし、小さい方からn-k個の総和
    vector<int> diffs(n-1);
    rep(i, 0, n-1) {
        diffs[i] = as[i + 1] - as[i];
    }
    sort(diffs.begin(), diffs.end());
    int ans = 0;
    rep(i, 0, n-k) {
        ans += diffs[i];
    }
    cout << ans << endl;
}