#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF (int)1e18
#define endl '\n'
const int mod = 1000 * 1000 * 1000 + 7;
const int N = 100005;
#define f first
#define s second
#define rep(i, a, b) for(int i = (a); i < (b); i++)
#define rrep(i, a, b) for(int i = (a); i > (b); i--)
#define vi vector<int>
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
void Solve() {
int n , k;
cin>>n>>k;
vi a(n);
for(int i = 0 ; i < n ;i++){
cin>>a[i];
}
vi diff;
for (int i = 0; i < n - 1; ++i) {
diff.push_back(a[i+1]-a[i]-1);
}
sort(all(diff));
int ans = n;
int moves = n;
int idx = 0;
while(moves>k){
ans += diff[idx++];
moves--;
}
cout<<ans<<endl;
}
int32_t main() {
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(false);
cin.tie(0);
int t = 1;
// cin >> t;
for (int i = 1; i <= t; i++) {
//cout << "Case #" << i << ": ";
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
