#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cmath>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<unordered_map>
#include<unordered_set>
using namespace std;
using ll = long long;
ll mod = 1e9 + 7;
ll gcd(ll a, ll b) {
if (b != 0) {
return gcd(b, a % b);
}
else return a;
}
ll lcm(ll a, ll b) {
return a * b / gcd(a, b);
}
ll pv(ll a, ll b) {
if (b == 0)return 1;
ll res = pv(a, b / 2) % mod;
if (b % 2 == 1) {
return ((res * res) % mod * a) % mod;
}
else return (res * res) % mod;
}
void solve() {
ll n, k; cin >> n >> k;
vector<ll>v(n);
for (ll i = 0; i < n; i++) {
cin >> v[i];
}
ll sum = v[n - 1];
vector<ll>a;
sort(v.begin(), v.end());
for (ll i = 0; i < n - 1; i++) {
a.push_back(v[i + 1] - v[i] - 1);
}
sort(a.rbegin(), a.rend());
for (ll i = 0; i < k - 1; i++) {
sum -= (a[i]);
}
cout << sum << endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
cout.tie(nullptr);
ll t = 1;
//cin >> t;
while (t--) {
solve();
}
}
