#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>

template <class T>
using MaxHeap = std::priority_queue<T>;

using lint = long long;

void solve() {
    int n, k;
    std::cin >> n >> k;

    std::vector<lint> xs(n);
    for (auto& x : xs) std::cin >> x;
    std::sort(xs.begin(), xs.end());

    lint ans = xs.back() - xs.front();
    MaxHeap<lint> heap;
    for (int i = 0; i + 1 < n; ++i) {
        heap.push(xs[i + 1] - xs[i]);
    }

    --k;
    while (k--) {
        ans -= heap.top();
        heap.pop();
    }

    std::cout << ans << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}