#include <stdio.h>
#include <deque>

using namespace std;

FILE*f=fopen("deque.in","r");
FILE*g=fopen("deque.out","w");

deque<int> d;

int v[5000020];

int main()
{
    int n,k,i;
    long long s=0;
    fscanf(f,"%d%d",&n,&k);
    for (i=1;i<=n;i++)
    {
        fscanf(f,"%d",&v[i]);
        while (!d.empty()&&v[d.back()]>=v[i]) d.pop_back();
        d.push_back(i);
        if (d.front()==i-k) d.pop_front();
        if (i>=k) s+=v[d.front()];
    }
    fprintf(g,"%lld",s);
    fclose(f);
    fclose(g);
    return 0;
}