#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include "bits/stdc++.h"
#define int long long
#define endl '\n'
#define Bismillah ios_base::sync_with_stdio(0);cin.tie(0);
#define indexed_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
using namespace __gnu_pbds;
const int N = 1e5 + 7;
const int INF = 1e18;
const int MOD = 998244353;
int n , k , a[N];
signed main()
{
Bismillah;
// freopen("closing.in", "r", stdin);
// freopen("closing.out", "w", stdout);
cin >> n >> k;
for(int i = 1; i <= n; i++)
{
cin >> a[i];
}
int say = 1;
for(int i = 2; i <= n; i++)
{
if(a[i] - a[i - 1] > 1) say++;
}
if(k >= say)
{
cout << n << endl;
return 0;
}
int res = n;
vector < int > v;
for(int i = 2; i <= n; i++)
{
if(a[i] - a[i - 1] == 1)continue;
v.push_back(a[i] - a[i - 1]);
}
sort(v.begin() ,v.end());
for(int i = 0; i < (say - k); i++)
{
res += v[i] - 1;
}
cout << res << endl;
}
