#include <bits/stdc++.h>
using namespace std;
#define level_up ios::sync_with_stdio(false);cout.tie(nullptr)
#define int long long
#define pb push_back
#define mk make_pair
#define ent cout << '\n'
#define F first
#define S second
#define all(s) s.begin(), s.end()
#define ERR cout << "ERROR\n";
#define yes cout << "YES\n"
#define no cout << "NO\n"
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
string alphabet = "abcdefghijklmnopqrstuvwxyz";
string num = "123456789";
string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int ITERATIONS = 1e7;
const int inf = 1e18;
const int N = 5e9+5;
const int NN = 5e15+10;
const int modd = 1e9+7;
const int k = 500;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void solve() {
int n, k;
cin >> n >> k;
int a[n+10];
for ( int i = 1; i <= n; i++ ) cin >> a[i];
int ans = n;
vector <int> v;
for ( int i = 2; i <= n; i++ ) {
v.pb(a[i] - a[i-1] - 1);
}
sort(all(v));
for ( int i = 0; i < n - k; i++ ) ans += v[i];
cout << ans;
}
signed main() {
level_up;
// freopen("bridges.in", "r", stdin);
// freopen("bridges.out", "w", stdout);
int T = 1;
// cin >> T;
for ( int test = 1; test <= T; test++ ) {
solve();
ent;
}
return 0;
}
