#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 1e5 + 5, inf = 1e9;
#define pb push_back
#define mp make_pair
#define ll long long
#define ff first
#define ss second
#define all(a) a.begin(),a.end()
#define sz(x) (int)x.size()
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int n, k;
cin >> n >> k;
vi a(n), b;
for(int i = 0; i < n; i++){
cin >> a[i];
if(i)b.pb(a[i] - a[i - 1] - 1);
}
ll ans = n;
sort(all(b));
for(int i = 0; i < n - k; i++){
ans += b[i];
}
cout << ans << '\n';
return 0;
}
