#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
#ifdef _DEBUG
#define dout(x) clog << "Line " << __LINE__ << ": " << #x << "=" << (x) << el
#else
#define dout(x)
#endif
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define uid(a,b) uniform_int_distribution<long long>(a,b)(rng)
#define ins insert
#define sz(x) (int((x).size()))
#define bs(args...) binary_search(args)
#define lb(args...) lower_bound(args)
#define ub(args...) upper_bound(args)
#define all(x) (x).begin(),(x).end()
#define mp(a, b) make_pair(a, b)
#define mt(args...) make_tuple(args)
#define pb push_back
#define eb emplace_back
#define f first
#define s second
#define die exit(0)
#define vc vector
#define rsz resize
#define as assert
template<typename T>
using uset = unordered_set<T>;
template<typename A, typename B>
using umap = unordered_map<A, B>;
template<typename T, typename Comp>
using pq = std::priority_queue<T, vc<T>, Comp>;
template<typename T>
using maxpq = pq<T, less<T>>;
template<typename T>
using minpq = pq<T, greater<T>>;
template<typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename A, typename B>
void cmin(A &x, const B &y) { x = min<common_type_t<A, B>>(x, y); }
template<typename A, typename B>
void cmax(A &x, const B &y) { x = max<common_type_t<A, B>>(x, y); }
using db = double;
using ld = long double;
using ll = long long;
using ull = unsigned long long;
using bi = __int128;
using ubi = unsigned __int128;
using pi = pair<int, int>;
using pll = pair<ll, ll>;
using pdb = pair<db, db>;
using pld = pair<ld, ld>;
using vb = vc<bool>;
using vi = vc<int>;
using vvi = vc<vi>;
using vll = vc<ll>;
using vpi = vc<pi>;
using vpll = vc<pll>;
using vpdb = vc<pdb>;
using vpld = vc<pld>;
using str = string;
constexpr char el = '\n';
constexpr char sp = ' ';
constexpr int inf = 0x3f3f3f3f;
constexpr ll llinf = 0x3f3f3f3f3f3f3f3fLL;
// ---------------------------------------------------------------------
const int N = 1e5+5;
int n, k, a[N];
signed main() {
ios::sync_with_stdio(0); cin.tie(0);
cout << fixed; clog << fixed; clog << unitbuf;
#ifndef _DEBUG
//freopen(".in", "r", stdin);
//freopen(".out", "w", stdout);
#endif
cin >> n >> k;
for(int i = 0; i < n; ++i)
cin >> a[i];
sort(a,a+n);
vi b;
for(int i = 1; i < n; ++i)
b.pb(a[i]-a[i-1]-1);
sort(all(b), greater<>());
int ans = a[n-1]+1-a[0];
for(int i = 0; i < k-1; ++i)
ans -= b[i];
cout << ans;
}
