学步园

#include<cstdio>
#include<cstring>
#include<cmath>
#include<iostream>
#include<cstdlib>
#define ll long long
#define inf 99999999999999LL
using namespace std;
int n,m,q[100002];
ll a[100002],sum,f[100002],mins=inf;
void dp()
{
	int t=0,w=0;
	for(int i=1;i<=n;i++)
       {f[i]=a[i]+f[q[t]];
        while(f[q[w]]>f[i]&&t<=w) w--;
        q[++w]=i;
        while(q[t]<i-m) t++;
       }
}
int main()
{
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;i++)
	   {scanf("%lld",&a[i]); sum+=a[i];}
	dp();
	for(int i=n-m;i<=n;i++) mins=min(mins,f[i]);
	printf("%lld",sum-mins);
	return 0;
	
}