#include <iostream>
#include <iomanip>
#include <utility>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <cmath>
#include <cstdint>
using namespace std;
int64_t n, k, a, last, diff[99999], ans;
int main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
cin >> n >> k >> last;
for (int i = 0; i < n - 1; i++){
cin >> a;
diff[i] = a - last - 1;
last = a;
}
sort(diff, diff + n - 1);
ans = n;
for (int i = 0; i < n - k; i++) ans += diff[i];
cout << ans;
}
