#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define stdI freopen("input.txt", "r", stdin);
#define stdO freopen("output.txt", "w", stdout);
#define all(x) x.begin(), x.end()
#define mp(x, y) make_pair(x, y)
#define int long long
#define F first
#define S second
using namespace std;
using namespace __gnu_pbds;
typedef tree<int,
null_type,less<int>,
rb_tree_tag,
tree_order_statistics_node_update> ordered_set;
typedef pair<int, int> pii;
const int MAXN = 2e5 + 100, INF = 1e18, MOD = 1e9 + 7;
void solve()
{
vector<pii> v;
int n, k;
cin >> n >> k;
int a[n];
for(int i = 0; i < n; i++)
{
cin >> a[i];
}
sort(a, a + n);
for(int i = 1; i < n; i++)
{
v.push_back(mp(a[i] - a[i - 1] - 2, i));
}
set<int> s; k--;
sort(all(v));
int ans = 0; s.insert(0);
while(v.size() > 0 && k > 0)
{
pii x = v.back(); v.pop_back(); k--;
ans += x.F;
s.insert(x.S);
}
cout << a[n - 1] + 2 - a[0] - s.size() - ans << "\n";
}
int32_t main()
{
IOS;
int t = 1;
//cin >> t;
while(t--)
{
solve();
}
return 0;
}
