#include <bits/stdc++.h>
#define int long long
#define vtr vector
#define vi vtr<int>
#define ii pair<int, int>
#define fi first
#define se second
#define len(s) (int)s.size()
#define fd(v, s, e) for (int v = s; v < e; ++v)
#define bk(v, s, e) for (int v = s-1; v >= e; --v)
#define farr(i, arr) for (auto i: arr)
#define all(arr) arr.begin(), arr.end()
using namespace std;
void presolve()
{
}
void solve()
{
int n, k; cin >> n >> k;
--k;
vi a(n);
farr (&i, a) cin >> i;
vi d;
fd (i, 1, n) d.emplace_back(a[i] - a[i-1]);
int ans = a[n-1] - a[0] + 1;
sort(all(d), greater<int>());
fd (i, 0, k) ans -= d[i] - 1;
cout << ans;
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int Tc = 1; // cin >> Tc;
auto S = chrono::high_resolution_clock::now();
presolve();
for (int T = 1; T <= Tc; ++T)
{ solve(); cout << '\n'; }
auto F = chrono::high_resolution_clock::now();
double TC = chrono::duration_cast<chrono::microseconds>(F - S).count();
cerr << setprecision(6) << fixed
<< "\nExecution time: " << TC * (1e-6) << " sec\n";
return 0;
}
