#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
using namespace std;
typedef long long ll;
const int MAXN = 1e6 + 7;
const int INF = 1e9 + 7;
int main()
{
ios_base::sync_with_stdio(0), cin.tie(0);
int n, k;
cin >> n >> k;
int prv_t = -1e9;
vector<int> smallest;
for (int i = 0; i < n; ++i) {
int t;
cin >> t;
smallest.pb(t - prv_t - 1);
prv_t = t;
}
sort(smallest.begin(), smallest.end());
int ans = n;
for (int i = 0; i < n - k; ++i)
ans += smallest[i];
cout << ans << '\n';
return 0;
}
