#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e6 + 100;
ll a[N];
ll solve() {
ll n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
sort(a + 1, a + 1 + n);
ll ans = a[n] - a[1] + 1;
vector <ll> lst;
for (int i = 2; i <= n; i++) {
lst.pb(a[i] - a[i - 1]);
}
sort(all(lst), greater <ll> ());
for (int j = 0; j < k - 1; j++) {
ans -= lst[j];
}
return ans + (k - 1);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
//cin >> t;
while (t--) {
//solve();
cout << solve() << '\n';
}
}
