#include <bits/stdc++.h>
using namespace std;
signed main() {
std::ios::sync_with_stdio(0);
std::cout.tie(0);
std::cin.tie(0);
#ifdef saarang
freopen("/home/saarang/Documents/cp/input.txt", "r", stdin);
freopen("/home/saarang/Documents/cp/output.txt", "w", stdout);
#endif
int n, k;
cin >> n >> k;
vector<long long> a(n), d;
for(auto &x : a)
cin >> x;
for(int i = 1; i < n; i++)
d.push_back(a[i] - a[i - 1] + 1);
sort(d.begin(), d.end(), greater<>());
long long ans = a.back() - a[0] + 1;
for(int i = 0; i < min(k - 1, (int) d.size()); i++)
ans -= d[i];
cout << ans << '\n';
return 0;
}
