#include <bits/stdc++.h>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define sz(x) (int)x.size()
//#define int ll
using namespace std;
typedef long long ll;
typedef long double ld;
const int N = (int)4e5 + 123;
const int mod = 1e9 + 7;
const ll inf = 1e18 + 9;
inline void boost () {
ios_base::sync_with_stdio (0);
cin.tie (0), cout.tie (0);
}
int n, k, t[N], pr[N], sz[N], all = n;
ll sum;
int get (int x) {
if (x == pr[x]) return x;
return pr[x] = get (pr[x]);
}
void unite (int u, int v, int c) {
if (all == k) cout << sum, exit (0);
u = get (u), v = get (v);
if (u == v) return;
if (sz[u] < sz[v]) swap (u, v);
sz[u] += sz[v];
pr[v] = u;
sum += c;
all --;
if (all == k) cout << sum, exit (0);
}
int main () {
boost ();
cin >> n >> k;
all = n, sum = k;
for (int i = 1;i <= n;i ++) {
cin >> t[i];
pr[i] = i, sz[i] = 1;
}
vector < pair < int, int > > v;
for (int i = 2;i <= n;i ++) v.pb (mp (t[i] - t[i - 1], i - 1));
sort (v.begin (), v.end ());
for (int i = 0;i < sz (v);i ++) {
int u = v[i].S;
int u1 = u + 1;
int c = v[i].F;
unite (u, u1, c);
}
cout << sum;
return 0;
}
