#include <bits/stdc++.h>
#define lli long long int
using namespace std;
lli n,k;
vector<lli> guests;
vector<lli> diff;
bool myopmyop(lli a, lli b) {
return a < b;
}
int main() {
cin >> n >> k;
lli totaldiff = 0;
for (lli i=0; i<n; i++) {
lli a;
cin >> a;
guests.push_back(a);
if (i >= 1) {
diff.push_back(guests[i] - guests[i-1] - 1);
// cout << guests[i] - guests[i-1] - 1<< " ";
totaldiff += guests[i] - guests[i-1] - 1;
}
}
sort(diff.begin(), diff.end(), myopmyop);
for (lli j=0; j<k-1; j++) {
totaldiff -= diff.back();
diff.pop_back();
}
//cout << endl << endl;
cout << totaldiff + n << endl;
}
