#include <bits/stdc++.h>
#define int long long
#define arr2 array<int, 2>
#define popcount __builtin_popcount
#define ctz __builtin_ctz
using namespace std;
const int N = 2e5;
void fun() {
int n, k;
cin >> n >> k;
int arr[n];
for (int i = 0; i < n; ++i) {
cin >> arr[i];
}
sort(arr, arr + n);
vector<int> boz;
for (int i = 1; i < n; ++i) {
boz.push_back(arr[i] - arr[i - 1] - 1);
}
sort(boz.begin(), boz.end());
int sum = 0;
for (int i = 0; i < (n - k); ++i) {
sum += boz[i];
}
cout << n + sum << "\n";
}
int32_t main() {
ios::sync_with_stdio(0);
cout.tie(0);
cin.tie(0);
// int tc;
// cin >> tc;
// while (tc--)
fun();
}
