#include <bits/stdc++.h>
using namespace std;
int n, k, a, totalSum;
vector<int> arrivals;
vector<int> diffs;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> k;
for (int i = 0; i < n; i++) {
cin >> a;
arrivals.push_back(a);
}
totalSum = arrivals[n-1] - arrivals[0] + 1;
for (int i = 1; i < n; i++) {
diffs.push_back(arrivals[i] - arrivals[i-1] -1);
}
sort(diffs.begin(), diffs.end());
for (int i = n-2; i > n-1-k; i--) {
totalSum -= diffs[i];
}
cout << totalSum;
}
