#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
using uint = unsigned;
using ull = unsigned long long;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
uint n, k;
cin >> n >> k;
vector<uint> a(n);
for (uint i = 0; i < n; i++) {
cin >> a[i];
}
sort(a.begin(), a.end());
vector<uint> t(n - 1);
for (uint i = 0; i + 1 < n; i++) {
t[i] = a[i + 1] - a[i] - 1;
}
sort(t.begin(), t.end());
ull lenght = n;
k--;
for (uint i = 0; i < n - k; i++) {
lenght += t[i];
}
cout << lenght << '\n';
}
