#include <iostream>
#include<fstream>
#define N 5000005
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");


int st,dr;
int a[N],n,k;

struct stiva
{
    int val,poz;
}s[N];

/*3
-1 -2 3 3 0 -1 4

-2 0
2 5

-2 */
void solve()
{
    int i,sum=0;
    for(i=1;i<=n;++i)
    {
        while(a[i]<s[dr].val&&dr>=st)
        dr--;
        s[++dr].val=a[i];
        s[dr].poz=i;
        if(s[dr].poz-s[st].poz==k)
            st++;
        if(i>=k)sum+=s[st].val;

    }
    fout<<sum;
}



int main()
{
    int i;
   fin>>n>>k;
   for(i=1;i<=n;++i)
    fin>>a[i];
    solve();

    return 0;
}