/**
* title: Stove
**/
#include <bits/stdc++.h>
using namespace std;
template <class T> istream &operator>>(istream &is, vector<T> &v) { for (auto &x : v) is >> x; return is; }
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) { auto sep = ""; for (auto &x : v) os << exchange(sep, " ") << x; return os; }
template <class T> vector<T> &operator+=(vector<T> &v, const T &a) { for (auto &x : v) x += a; return v; }
template <class T> vector<T> &operator-=(vector<T> &v, const T &a) { for (auto &x : v) x -= a; return v; }
template <class T, class U> inline bool chmax(T &a, const U &b) { return (a < b ? a = b, 1 : 0); }
template <class T, class U> inline bool chmin(T &a, const U &b) { return (b < a ? a = b, 1 : 0); }
#define si(x) int(x.size())
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second
using ll = long long;
constexpr int inf = 1001001001;
constexpr long long infll = 4004004004004004004LL;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int N, K;
cin >> N >> K;
vector<int> T(N);
cin >> T;
vector<int> V;
for (int i = 0; i + 1 < N; i++) {
V.push_back(T[i + 1] - T[i] - 1);
}
sort(all(V));
int ans = N;
for (int i = 0; i < N - K; i++) {
ans += V[i];
}
cout << ans << '\n';
}
