#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define sort undefined_function // To use stable_sort instead sort
#define bpc __builtin_popcount
#define ull unsigned long long
#define ld double
#define ll long long
#define mp make_pair
#define F first
#define S second
# pragma GCC optimize("O2")
//pragma GCC optimize("my solution")
using namespace __gnu_pbds;
using namespace std;
typedef tree<long long, null_type, less_equal<long long>,
rb_tree_tag, tree_order_statistics_node_update> Tree;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll INF = 9223372036854775807LL;
const ll inf = 2147483647;
const ll MOD = 1e9 + 7; //[998244353, 1e9 + 7, 1e9 + 13]
ll gcd(ll a, ll b) {return b ? gcd(b, a % b) : a;}
ll lcm(ll a, ll b) {return a * b / gcd(a, b);}
ll ceil(ll a, ll b) {return (a + b - 1) / b;}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<ll> v(n + 1);
for (int i = 1; i <= n; i ++)
cin >> v[i];
vector<ll> aux;
for (int i = 1; i < n; i ++)
aux.push_back(v[i + 1] - v[i] - 1);
k --;
stable_sort(aux.begin(), aux.end());
while (k --)
aux.pop_back();
ll ans = n;
for (auto &x : aux)
ans += x;
cout << ans << '\n';
return 0;
}
