#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
#define endl '\n'
int main() {
#ifdef mlocal
freopen("test.in", "r", stdin);
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k; cin >> n >> k;
vector<ll> nums(n);
for_(i, 0, n) cin >> nums[i];
sort(nums.begin(), nums.end());
ll ans = 0;
vector<ll> gap;
for_(i, 1, n) gap.push_back(nums[i]-nums[i-1]-1);
sort(gap.begin(), gap.end(), greater<>());
for_(i, 0, k-1) ans += gap[i];
cout << nums.back()+1-nums[0]-ans << endl;
return 0;
}
