#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
int main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
#endif
ios::sync_with_stdio(false);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<int> t(n);
for (int i = 0; i < n; ++i) cin >> t[i];
ll need = t[n - 1] - t[0] + 1;
vector<int> arr;
for (int i = 1; i < n; ++i) arr.push_back(t[i] - t[i - 1] - 1);
sort(arr.rbegin(), arr.rend());
for (int i = 0; i < k - 1; ++i) need -= arr[i];
cout << need << endl;
return 0;
}
