#include <cstdio>
#include <deque>

using namespace std;

FILE * iFile;
FILE * oFile;

long long n, k, x, minim, s;
deque<long long> deq;

long long minim_from_deq()
{
    long long minimum=100, i;
    for(i=0;i<k;i++)
    {
        if(deq[i] < minimum)
            minimum = deq[i];
    }
    return minimum;
}

int main()
{
    iFile = fopen("deque.in", "r");
    oFile = fopen("deque.out", "w");

    long long i;

    fscanf(iFile, "%lld %lld", &n, &k);

    for(i=1;i<=n;i++)
    {
        fscanf(iFile, "%lld", &x);
        deq.push_back(x);
        if(i >= k)
        {
            minim = minim_from_deq();
            deq.pop_front();
            s = s + minim;
        }

    }

    fprintf(oFile, "%lld ", s);

    fclose(iFile);
    fclose(oFile);

    return 0;
}