#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <fstream>
#include <deque>
#define MAXX 5000005
#include <stack>
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
int a1,a2,a3,k,amax,V[MAXX],Arr[MAXX];
int N,K,cnt;
long long sum,st=1,dr;

int main()
{
    f >> N >> K;
    for ( int i=1; i<=N; i++ )
        f >> V[i];
    for ( int i=1; i<=N; i++ )
    {
        while ( st<=dr and V[Arr[dr]]>=V[i] and dr>0 )
            dr = dr-1;
        Arr[++dr] = i;
        if ( st<=dr and i-K == Arr[st] )
            st = st+1;
        if ( K<=i )
            sum = sum+V[Arr[st]];
    }
    g << sum;
    return 0;
}