#include <bits/stdc++.h>
#define ff first
#define ss second
#define cont continue;
#define sz size()
#define pb push_back
using namespace std;
typedef long long ll;
const int N = 100005;
void solve();
int n, k, a[N], jogap;
vector <int> v;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
cin >> n >> k;
for (int i = 1; i <= n; ++i) {
cin >> a[i];
}
for (int i = 1; i < n; ++i) {
v.pb (a[i + 1] - a[i] - 1);
}
sort (v.begin(), v.end());
for (int i = 0; i < n-k; ++i) {
jogap += v[i];
}
cout << n + jogap << "\n";
return 0;
}
