#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int N, K;
cin >> N >> K;
vector<long long> T(N);
for (int i = 0; i < N; ++i) cin >> T[i];
if (K >= N) {
cout << N << "\n";
return 0;
}
vector<long long> gaps;
gaps.reserve(N - 1);
for (int i = 0; i + 1 < N; ++i) {
long long g = T[i+1] - T[i] - 1; // jarak dari akhir tamu i ke awal tamu i+1
// karena "paling banyak satu tamu pada satu waktu", g >= 0
gaps.push_back(g);
}
sort(gaps.begin(), gaps.end()); // naik
long long extra = 0;
int needMerge = N - K;
for (int i = 0; i < needMerge; ++i) extra += gaps[i];
long long ans = (long long)N + extra;
cout << ans << "\n";
return 0;
}
