#include <bits/stdc++.h> using namespace std; int n, k; int a[100100]; int main() { ios_base::sync_with_stdio(false);cin.tie(nullptr); cin >> n >> k; for (int i = 1; i <= n; ++i) cin >> a[i]; int sum = a[n] - a[1] + 1; for (int i = 1; i < n; ++i) a[i] = a[i + 1] - 1 - a[i]; --n; sort(a + 1, a + 1 + n, greater<int> ()); for (int i = 1; i < k; ++i) sum -= a[i]; cout << sum; return 0; }