#include<bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define LC ch[k][0] 
#define RC ch[k][1]
#define IO cin.sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define rep(i,a,n) for (int i = a; i < n; i++)
#define repn(i,a,n) for (int i = a; i <= n; i++)
#define per(i,a,n) for (int i = n - 1; i >= a; i--)
#define pern(i,a,n) for (int i = n; i >= a; i--)

typedef long long LL;
typedef unsigned long long ull;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;

const int N = 100010;
const int M = 610000;
const int mod = 1e9+7;
const int inf = (int)1e9;
const LL INF = (LL)1e18;
const double eps = 1e-9;

int n, a, t[N], b[N]; 
int main()
{
	IO;
	cin >> n >> a;
	int num, cnt = 0;
	repn(i, 1, n) {
		cin >> num;
		if (num == 0) {
			t[i] ++;
			t[(i % n) + 1] ++;
			t[((i + n - 2) % n) + 1] ++;
		} 
		else cnt ++;
	}
	sort(t + 1, t + n + 1);
	int ans = 0;
	pern(i, a + 1, n) {
		ans += t[i];
	} 
	ans += 3 * cnt;
	cout << ans << "\n";
	return 0;
}