#include <bits/stdc++.h>
#define int long long
#define ii pair<int, int>
using namespace std;
#define inf 1e18
void fast_io()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
}
void solve()
{
int n, k;
cin >> n >> k;
vector <int> arr(n), oraliq;
for(int &i: arr) cin >> i;
sort(arr.begin(), arr.end());
int ans = abs(arr[0]-arr[n-1])+1;
for(int i = 1; n > i; i++){
oraliq.push_back(arr[i]-arr[i-1]-1);
}
sort(oraliq.rbegin(), oraliq.rend());
for(int i = 0; k-1 > i; i++){
ans -= oraliq[i];
}
cout << ans << '\n';
}
signed main()
{
fast_io();
clock_t start = clock();
int t = 1;
// cin >> t;
while (t--)
{
solve();
}
cerr << "\n\n"
<< "Vaqt " << (double)(clock() - start) * 1000.0 / CLOCKS_PER_SEC << " ms\n";
return 0;
}
