#include <bits/stdc++.h>
using namespace std;
void solve() {
long long n,k; cin >> n >> k;
vector<long long> ans(n);
// ans.push_back(0);
// ans.push_back(1e9);
for(int i= 0;i < n;i++){
cin >> ans[i];
}
sort(ans.begin(),ans.end());
int need = n - k;
//int m = ans.size();
vector<long long> diff;
int output = n;
for(int i =1;i < n;i++){
diff.push_back(max(0LL,ans[i] - ans[i - 1] - 1));
}
sort(diff.begin(),diff.end());
for(int i= 0;i < min((int)diff.size(),need);i++){
if(diff[i] > 0)
output+=diff[i];
}
cout << output << endl;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int t = 1;
// cin >> t;
while (t--) solve();
}
