#include<bits/stdc++.h>
using namespace std;using ll=long long;const ll inf=1e17;
struct S
{
	vector<int>a,b;
	void solve()
	{
		int n,k,res=0;cin>>n>>k;a.resize(n),b.resize(n);for(auto &k:a)cin>>k,res+=k*3;
		for(int i=0;i<n;i++)b[i]=a[i]+a[(i+1)%n]+a[(i+n-1)%n];
		sort(b.begin(),b.end());for(int i=0;i<n-k;i++)res+=3-b[i];cout<<res<<'\n';
	}
};
int main()
{
	//freopen("3.in","r",stdin);
	//cout<<fixed<<setprecision(12);
	ios::sync_with_stdio(0);cin.tie(0);
	int t=1;//cin>>t;
	//clock_t a=clock();
	while(t--){S SS;SS.solve();}
	//cout<<"Time:"<<double(clock()-a)<<'\n';
}