//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
#include<bits/stdc++.h>
using namespace std;
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define sz(a) (int)a.size()
#define s second
#define f first
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
vector<pii> rid = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
vector<pii> dir = {{-1, -1}, {-1, 1}, {1, -1}, {1, 1}};
const int N = 1e6 + 1, mod = 1e9 + 7;
const ll inf = 1e9;
double eps = 1e-15;
bool flg = 0;
void slv() {
int n, k;
cin >> n >> k;
int t[n + 1];
for (int i = 1; i <= n; i++) {
cin >> t[i];
}
sort(t + 1, t + n + 1);
int ans = t[n] - t[1] + 1;
vector<int> s;
for (int i = 1; i < n; i++) {
s.push_back(t[i + 1] - t[i] - 1);
}
sort(rall(s));
for (int i = 0; i < k - 1; i++) ans -= s[i];
cout << ans;
}
main() {
//freopen("rsq.in", "r", stdin);
//freopen("rsq.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int tp = 1;
if (flg) cin >> tp;
while (tp--) {
//cout << "Case #" << cur++ << ": ";
slv();
}
}
//wenomechainsama
