#include <iostream>
#include <queue>
#include <algorithm>
using namespace std;
const int N = 1e5 + 5;
int a [N];
int main () {
ios::sync_with_stdio(0);
int n, k;
cin >> n >> k;
for (int i = 0; i < n; i++) cin >> a[i];
sort (a, a + n);
int res = a[n - 1] - a[0] + 1;
--k;
vector<int> dis;
int rem = 0;
for (int i = 1; i < n; i++) {
dis.emplace_back(a[i] - a[i - 1] - 1);
}
sort (dis.rbegin(), dis.rend());
for (int i = 0; i < min (k, (int) dis.size()); i++) {
rem += dis[i];
}
cout << res - rem << '\n';
return 0;
}
