#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
	int n, m;
	cin >> n >> m;
	vector<int> a(n + 1), b(n + 1);
	for(int i = 1; i <= n; i ++) cin >> a[i];
	ll ans = n * 3ll;
	for(int i = 1; i <= n; i ++) {
		if(i > 1 && i < n)
		b[i] = (3 - a[i] - a[i - 1] - a[i + 1]);
		else if(i == 1) {
			b[i] = (3 - a[1] - a[n] - a[2]);
		} else {
			b[i] = (3 - a[n] - a[1] - a[n - 1]);
		}
	}
	sort(b.begin() + 1, b.end());
	for(int i = 1; i <= m; i ++) {
		ans -= b[i];
	}
	cout << ans;

}