#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define fi first
#define se second
#define banyak int tc = 1; cin >> tc; while(tc--){solve();}
#define vector2d(x) vector<vector<x>>
#define pii pair<int, int>
#define pl pair<ll, ll>
#define kagamine_len ios_base::sync_with_stdio(0); cin.tie(0);
#define file_in freopen("input.txt", "r", stdin);
#define file_out freopen("output.txt", "w", stdout);
#define all(x) x.begin(), x.end()
using namespace std;
int main(){
kagamine_len
ll n, k; cin >> n >> k;
vector<ll> ar(n+2, 0);
priority_queue<ll> pq;
for (ll i = 1; i <= n; i++) cin >> ar[i];
ar[n+1] = 1e9+69;
sort(all(ar));
ll tot = ar[n] - ar[1] + 1, ans = tot;
for (ll i = 2; i <= n; i++){
pq.push(ar[i]-ar[i-1]);
}
k--;
while(!pq.empty() && k--){
ll cur = pq.top();
pq.pop();
// cout << cur << "\n";
tot = tot - cur + 1;
ans = min(ans, tot);
}
cout << ans << "\n";
return 0;
}
