#include <bits/stdc++.h>
#define ll long long
#define ar array
#define db double
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define rint(l, r) uniform_int_distribution<int>(l, r)(rng)
template<typename T> bool ckmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<typename T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }
void test_case() {
int n, k;
cin >> n >> k;
vector<int> a(n);
for (int &x : a) cin >> x;
int ans = a.back() - a[0] + 1;
vector<int> gaps;
for (int i = 1; i < n; i++) gaps.emplace_back(a[i] - a[i-1] - 1);
sort(all(gaps), greater());
for (int i = 0; i < k-1; i++) ans -= gaps[i];
cout << ans << '\n';
}
int main() {
cin.tie(0)->sync_with_stdio(0);
int t = 1;
// cin >> t;
while (t--) test_case();
}
