#include <bits/stdc++.h>
#define int int64_t
using namespace std;
int32_t main(){
int n, k; cin >> n >> k;
vector<int> a(n);
for(int i = 0; i < n; i++) cin >> a[i];
sort(a.begin(), a.end());
vector<pair<int, int>> dist;
dist.reserve(n);
for(int i = 1; i < n; i++){
dist.push_back({a[i]-a[i-1], i-1});
}
sort(dist.begin(), dist.end(), greater<pair<int, int>>());
set<int> cutoff;
for(int i = 0; i < k-1; i++){
//cout << dist[i].first << ":" << dist[i].second << '\n';
cutoff.insert(dist[i].second);
}
int ans = 0;
int curr = a[0];
for(int i = 0; i < n; i++){
if(cutoff.count(i) || i==n-1){
ans+=a[i]+1-curr;
if(i!=n-1) curr=a[i+1];
}
}
cout << ans;
return 0;
}
