#include <bits/stdc++.h>
using namespace std;
#define int long long
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
void Solve()
{
int n, k;
cin>>n>>k;
int canskip = k - 1;
int t[n];
for (int i=0; i<n; i++)
cin>>t[i];
int d[n-1];
sort(t, t+n);
for (int i=0; i<n-1; i++)
{
d[i] = t[i+1] - t[i] - 1;
}
sort(d, d+n-1, greater<int>());
int val = t[n-1] - t[0] + 1;
for (int i=0; i<canskip; i++)
{
val -= d[i];
}
cout<<val;
}
int32_t main()
{
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
//cin >> t;
for(int i = 1; i <= t; i++)
{
//cout << "Case #" << i << ": ";
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
