#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <deque>
#include <map>
#include <set>
#include <complex>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <random>
#define ft first
#define sc second
#define pb push_back
#define len(v) (int)v.size()
#define int ll
using namespace std;
typedef long long ll;
signed main() {
#ifdef PC
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k, ans, pr = -1;
cin >> n >> k;
ans = n;
vector<int> can;
for (int i = 0; i < n; i++) {
int t;
cin >> t;
if(i > 0)
can.pb(t - pr);
pr = t + 1;
}
sort(can.begin(), can.end());
for (int i = 0; i < (n - k); i++)
ans += can[i];
cout << ans << endl;
return 0;
}
