#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vi;
typedef pair<ll, ll> pi;
#define FOR(i, j, k) for (ll i = j; i < (ll) k; ++i)
#define FORD(i, j, k) for (ll i = j; i >= (ll) k; --i)
#define nl "\n"
#define sp " "
#define all(x) (x).begin(), (x).end()
#define sc second
#define fr first
#define pb emplace_back
const ll inf = 1e15;
void solve()
{
ll n, k;
cin >> n >> k;
ll a[n];
FOR(i, 0, n)
cin >> a[i];
ll total = a[n - 1] + 1 - a[0];
vi diff;
FOR(i, 1, n) {
diff.pb(a[i] - a[i - 1] - 1);
}
/* for(auto i : diff) */
/* cout << i << sp; */
/* cout << nl; */
sort(all(diff));
reverse(all(diff));
FOR(i, 0, min((ll) diff.size(), k - 1)) {
total -= diff[i];
}
cout << total << nl;
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t = 1;
// cin >> t;
while (t--)
{
solve();
}
}
