#include <iostream>
#include <deque>

using namespace std;


int main()
{
    int d[25],a[25],n,k,poz[25],i,s=0;
    cin>>n>>k;
    for(i = 1; i <=n; i++)
        cin>>a[i];
    int pr = 0;
    int ul = -1;
    for(i = 1; i <=k; i++)
    {
        int x = a[i];
        while(pr<=ul && d[ul] >=x)
            ul--;
        d[++ul] = x;
        poz[ul] = i;
    }
    s=s+d[pr];
    for( i = k+1; i <=n; i++)
    {
        int x = a[i];
        while(pr <=ul && d[ul] >=x) ul--;
        d[++ul] = x;
        poz[ul] = i;
        if(poz[pr]<= i-k) pr++;
        s+=d[pr];
    }
    cout<<s;

    return 0;
}