#include <bits/stdc++.h>
using namespace std;
// Templates
// ==============================================
// Debugging
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif
typedef long long ll;
typedef vector<int> VI;
typedef vector<long long> VLL;
typedef vector<bool> VB;
typedef vector<vector<int>> VVI;
typedef pair<int, int> PI;
typedef pair<ll, ll> PLL;
typedef vector<pair<int, int>> VPI;
#define pb push_back
#define ff first
#define ss second
#define loop(i, s, e) for (int i = s; i < e; ++i)
#define inp(v) for (auto& x : v) cin >> x
#define all(a) a.begin(), a.end()
#define revall(a) a.rbegin(), a.rend()
#define nl "\n"
// #define MOD 998244353
#define MOD 1000000007
#define MAXN 300002
#define INF (int) 1e9
#define INFL (ll) 1e18
#define yep cout << "YES\n"
#define nope cout << "NO\n"
// ==============================================
void solve()
{
int n, k; cin >> n >> k;
VI a(n); inp(a);
VI interval;
loop(i, 1, n) interval.pb(a[i] - a[i - 1] - 1);
sort(revall(interval));
int ans = a[n - 1] - a[0] + 1;
loop(i, 0, k - 1) ans -= interval[i];
cout << ans << nl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
// cin >> t;
while(t--) solve();
#ifdef LOCAL
cerr << "Execution time: " << 1000.f * clock() / CLOCKS_PER_SEC << " ms." << nl;
#endif
return 0;
}
