#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF 9e18
void solve() {
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
sort(a.begin(), a.end());
a.erase(unique(a.begin(), a.end()), a.end());
n = a.size();
vector<int> gaps;
for (int i = 1; i < n; i++) {
gaps.push_back(a[i] - a[i - 1] - 1);
}
sort(gaps.rbegin(), gaps.rend());
int ans = (a[n - 1] + 1) - a[0];
for (int i = 0; i < k - 1; i++) {
ans -= gaps[i];
}
cout << ans;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
