#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main()
{
    int n, k;
    cin >> n >> k;
    
    vector<int> cost( n );
    int totalCost = 0;
    for( int i=0 ; i<n ; ++i )
    {
        cin >> cost[i];
        totalCost += cost[i];
    }
    
    if( k == 0 )
    {
        cout << totalCost << endl;
        return 0;
    }
    
    if( k >= (n-1)/2 )
        cout << cost[(n-1)/2] << endl;
    return 0;
}