// #pragma GCC target("avx2")
#pragma GCC optimize("O3", "unroll-loops")
// #include <bits/extc++.h>
// using namespace __gnu_pbds;
#include <bits/stdc++.h>
using namespace std;
#define int long long
// template <typename T>
// using pbds_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
using pii = pair<int, int>;
template<typename T>
using prior = priority_queue<T, vector<T>, greater<T>>;
template<typename T>
using Prior = priority_queue<T>;
#define X first
#define Y second
#define fastIO() ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define RANDOM() random_device __rd; \
mt19937 __gen = mt19937(__rd()); \
uniform_int_distribution<int> __dis(0, 1); \
auto rnd = bind(__dis, __gen);
const int INF = 1E18;
const int mod = 1E9 + 7;
int32_t main() {
fastIO();
int n, k;
cin >> n >> k;
int v[n], ans = n;
for (int i = 0; i < n; ++i) cin >> v[i];
for (int i = n-1; i >= 1; --i) v[i] = v[i] - v[i - 1] - 1;
sort(v + 1, v + n);
for (int i = 1; i <= n-k; ++i) ans += v[i];
cout << ans << "\n";
return 0;
}
