#include<bits/stdc++.h>
using namespace std;
int main(){
int n, k, a;
cin >> n >> k;
vector<int> guests;
vector<int> dif;
for(int i = 0; i < n; ++i){
cin >> a;
guests.push_back(a);
}
int t = guests[n-1]-guests[0]+1;
if(k == 1) {
cout << t << '\n';
exit(0);
}
if(k == n) {
cout << k << '\n';
exit(0);
}
for(int i = 1; i < n; ++i){
dif.push_back(guests[i] - guests[i-1]-1);
//cout << dif[i-1] << ' ';
} //cout << '\n';
sort(dif.begin(), dif.end());
reverse(dif.begin(), dif.end());
for(int i = 0; i < k; ++i){
t -= dif[i];
//cout << dif[i] << ' ';
} //cout << '\n';
cout << t << '\n';
return 0;
}
