#include <iostream>
#include <fstream>
using namespace std;

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

int a[5000009];
int Deque[5000008];
int n,k;

void Read()
{
    int i,j;
    int Front =0, Back = 0;
    long long total = 0;
    fin>>n>>k;
    for(i = 1; i<=n; ++i)
        fin>>a[i];
    for(i = 1; i<=n; ++i)
    {
        while( Front <= Back && a[i] <= a[ Deque[Back] ] )
            Back--;
        Deque[++Back] = i;
        if( Deque[Front] <= i-k )
            Front++;
        if( i>=k) total += a[ Deque[Front]];
    }
    fout<<total;
}

int main()
{
    Read();
    return 0;
}