#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define ll long long
const int MAX = 1e6 + 5, inf = 2e9;

int n, k;
int a[MAX], b[MAX];
void solve(){
    cin >> n >> k;
    int ans = 0;
    for (int i = 1; i <= n; ++ i) cin >> a[i];
    ans += (n - k) * 3;
    for (int i = 1; i <= n; ++ i){
        b[i] = a[i] + a[i % n + 1] + a[(i + n - 2) % n + 1];
    }
    sort(b + 1, b + n + 1);
    for (int i = 0; i < k; ++ i) ans += b[n - i];
    cout << ans;
}
int main(){
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	//int _;cin>>_;while (_ --)
		solve();
}