#include <iostream>
#include <string.h>
#include <algorithm>
 
using namespace std;
long long int dp[2][10003];
long long int data[10003];
int main() {
	// your code goes here
	int n,m;
	memset(dp,0,sizeof(dp));
	memset(data,0,sizeof(data));
	cin>>n>>m;
	for(int i=0;i<n;i++){
		cin>>data[i];
	}
	//ずっと頭がぼーっとして何も考えられない;
	for(int i=0;i<n;i++){
		dp[1][i]=max(dp[1][i],data[i]);
		long long int d=data[i];
		for(int j=0;j<=i;j++){
			if(j<=i-m+1){
				dp[1][i+1]=max(dp[1][i+1],dp[1][j]+d);
				dp[0][i+m]=max(dp[1][i+m],dp[1][j]+d);
			}else{
				dp[1][j+m]=max(dp[1][j+m],dp[1][j]+d);
				dp[0][i+m]=max(dp[0][i+m],dp[1][j]+d);
			}
			dp[1][i]=max(dp[1][i],dp[0][j]+d);
			dp[1][i+1]=max(dp[1][i+1],dp[0][j]+d);
		}	
 
		for(int j=0;j<2;j++){
			dp[j][i+1]=max(dp[j][i+1],dp[j][i]);
		}
 
		//for(int j=0;j<13;j++){
		//	cout<<j<<"("<<dp[0][j]<<" "<<dp[1][j]<<")";
		//}
		//cout<<endl;
	}
	long long int ans=0;
	for(int i=0;i<n*2+4;i++){
		for(int j=0;j<2;j++){
			ans=max(ans,dp[j][i]);
		}
	}
	cout<<ans<<endl;
	return 0;
}

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