#include <bits/stdc++.h> #define f first #define s second #define ii pair<int, int> #define iii pair<ii, int> #define pb push_back #define save_time ios_base::sync_with_stdio(false); cin.tie(NULL); const int inf = 1e9 + 7; using namespace std; bool comp(int a, int b) { return a > b; } int main() { save_time; int n, k; cin >> n >> k; vector<long long> v(n); for (auto &i : v) { cin >> i; } vector<long long> time(n - 1); for (int i = 0; i < n - 1; i++) { time[i] = v[i + 1] - v[i] - 1; } sort(time.begin(), time.end(), comp); long long ans = v[n - 1] - v[0] + 1; for (int i = 0; i < k - 1; i++) { ans -= time[i]; } cout << ans; }