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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    long long n,k,c[100000],min,i,x=0,x1=0;
    cin>>n>>k;
    if(k==1)
    {
        for(i=0;i<n;i++)
            cin>>c[i];
        for(i=0;i<n;i+=3)
            x+=c[i];
        for(i=1;i<n;i+=3)
            x1+=c[i];
        if(x<x1)
            min=x;
        else min=x1;
        
    }   
    else
    {    
    for(i=0;i<n;i++)
    cin>>c[i];
    min=c[k];
    for(i=k;i<n-k;i++)
    {
        if(c[i]<min)
            min=c[i];
        
    }
    }
    cout<<min;
    return 0;
}