/**
* Martin Leshko (leshko.martin@gmail.com)
*/
#include <bits/stdc++.h>
using namespace std;
#define forn(i, n) for (int i = 0; i < (int)n; i++)
#define sz(a) (int)a.size()
const int N = 300001;
int main() {
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int i = 0; i < n; i++)
cin >> a[i];
vector<int> sums;
for (int i = 1; i < n; i++)
if (a[i] - a[i - 1] > 1)
sums.push_back(a[i] - a[i - 1] - 1);
sort(sums.rbegin(), sums.rend());
int ans = a[sz(a) - 1] - a[0] + 1;
for (int i = 0; i < min(sz(sums), k - 1); i++)
ans -= sums[i];
cout << ans << endl;
}
