#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long int
#define endl '\n'
#define pb push_back
#define pi pair<int, int>
#define pii pair<int, pi>
#define fir first
#define sec second
#define MAXN 500001
#define mod 1000000007
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, k;
cin >> n >> k;
vector<int> v(n);
priority_queue<int, vector<int>, greater<int>> pq;
for (int i = 0; i < n; i++)
{
cin >> v[i];
if (i >= 1)
pq.push((v[i] - v[i - 1]) - 1);
}
int g = n, ans = n;
while (g > k)
{
ans += pq.top();
pq.pop();
g--;
}
cout << ans << endl;
return 0;
}
