#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
long long N, K;
cin >> N >> K;
vector<long long> T(N);
for (long long i = 0; i < N; ++i) {
cin >> T[i];
}
if (K >= N) {
cout << N << endl;
return 0;
}
vector<long long> a;
a.reserve(N-1);
for (long long i = 0; i+1 < N; ++i) {
long long g = T[i+1] - T[i] - 1;
a.push_back(g);
}
ranges::sort(a);
long long ans = N;
for (long long i = 0; i < N-K; i++) {
ans += a[i];
}
cout << ans << '\n';
return 0;
}
