//#pragma optimize("Ofast")
//#pragma optimize("unroll-loops")
//#pragma target("avx,avx2")
#include <iostream>
#include <cmath>
#include <algorithm>
#include <stdio.h>
#include <cstdint>
#include <cstring>
#include <string>
#include <cstdlib>
#include <vector>
#include <bitset>
#include <map>
#include <queue>
#include <ctime>
#include <stack>
#include <set>
#include <list>
#include <random>
#include <deque>
#include <functional>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <complex>
#include <numeric>
#include <cassert>
#include <array>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <thread>
typedef long long ll;
typedef long double ld;
using namespace std;
#define el '\n'
#define ff first
#define ss second
#define pb push_back
#define popb pop_back
#define point pair <ll, ll>
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
const ll N = 1e5 + 10;
const ll INF = 2e18 + 10;
const ll inf = 2e9 + 10;
void solve() {
ll n, k;
cin >> n >> k;
vector <ll> t(n);
for (ll i = 0; i < n; i++)
cin >> t[i];
vector <ll> b;
ll ans = n;
for (ll i = 1; i < n; i++)
b.pb(t[i] - t[i - 1] - 1);
sort(all(b));
for (ll i = 0; i < n - k; i++)
ans += b[i];
cout << ans << el;
return;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int tests = 1;
//cin >> tests;
while (tests--)
solve();
return 0;
}
