// source problem :
#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
#define int long long
#define lb lower_bound
#define ub upper_bound
#define MASK(i) (1LL << (i))
const int inf = 1e18;
void ckmax(int& f, int s)
{
f = (f > s ? f : s);
}
void ckmin(int& f, int s)
{
f = (f < s ? f : s);
}
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int &i : a) cin >> i;
sort(all(a));
k--;
vector<int> d;
for (int i = 1; i < n; i++) d.push_back(a[i] - a[i - 1] - 1);
sort(d.rbegin(), d.rend());
int ans = a[n - 1] - a[0] + 1;
for (int i = 0; i < k; i++) ans -= d[i];
cout << ans;
return 0;
}
