#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <ctime>
#include <bitset>
#include <complex>
#include <random>
using namespace std;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<int> a(n);
for (auto &t : a) {
cin >> t;
}
sort(a.begin(), a.end());
int ans = a.back() - a.front() + 1;
vector<int> dl;
for (int i = 1; i < n; i++) dl.push_back(a[i] - a[i - 1] - 1);
sort(dl.rbegin(), dl.rend());
for (int i = 0; i < k - 1; i++) ans -= dl[i];
cout << ans << endl;
}
