#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;

int a[N], b[N];

signed main()
{
    int n, m;
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; ++i) {
        scanf("%d", &a[i]);
    }
    for (int i = 1; i <= n; ++i) {
        b[i] = a[i] + a[i % n + 1] + a[(i + 1) % n + 1];
    }
    sort(b + 1, b + n + 1);
    int res = 3 * (n - m);
    for (int i = 1; i <= m; ++i) {
        res += b[n - i + 1];
    }
    printf("%d\n", res);
    return 0;
}