#include <bits/stdc++.h>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");


deque < int  > deq;




int main()
{
    int n;
    in>>n;
    int k;
    in>>k;
    int s=0;
    for(int x,i=1;i<=n;i++)
    {
        in>>x;
        deq.push_back(x);

    }
    for(int i=0;i<n;i++)
    {
        if(deq[0]<deq[1] and deq[0]<deq[2]){s+=deq[0];deq.pop_front();}
        else if(deq[1]<deq[0] and deq[1]<deq[2]){s+=deq[1];deq.pop_front();}
            else if(deq[2]<deq[0] and deq[2]<deq[1]){s+=deq[2];deq.pop_front();}

    }
    out<<s;

    in.close();
    out.close();
    return 0;
}