#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
int MOD = 1e9 + 7;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cout << fixed << setprecision(0);
ll n, k, ans = 0; cin >> n >> k;
vector<ll> a(n), b(n - 1); for (auto &x: a) cin >> x;
sort(a.begin(), a.end());
for (ll i = 0; i < n - 1; i++) b[i] = a[i + 1] - (a[i] + 1);
sort(b.begin(), b.end());
for (ll i = 0; i < n - 1 - (k - 1); i++) ans += b[i];
cout << ans + n;
}
