#include<cstdio>

#include<iostream>

#define ll long long

using namespace std;

//#pragma GCC optimize ("O3")

int n,k;

ll e[];

ll dp[];

ll sum[];

ll q[],head,tail;

ll num[];

long long calc(int a)

{

    num[a]=dp[a-]-sum[a];

    while(head<=tail && num[q[tail]]<num[a])tail--;

    q[++tail]=a;

    while(head<=tail && q[head]<a-k)head++;

    return num[q[head]];

}

//f[i]=max(f[i],f[j-1]-sum[j])+sum[i]    (j 1~e)

int main()

{

    scanf("%d%d",&n,&k);

    for(int i=;i<=n;i++){scanf("%lld",&e[i]);sum[i]=sum[i-]+e[i];}

    for(int i=;i<=n;i++)dp[i]=calc(i)+sum[i];

    cout<<dp[n];

}