#include<iostream.h>
#include<fstream.h>
int main()
{int i,n,k,a[100],max=-23000,j,s[100],y;
	ifstream f("secv2.in");
	ofstream h("secv2.out");
f>>n>>k;
for(i=1;i<=n;i++)
	f>>a[i];
for(i=1;i<n;i++)
{s[i]=a[i];
	for(j=i+1;j<i+k;j++)	
s[i]=s[i]+a[j];
}
for(i=1;i<=n-k;i++)
	{for(j=i+k;j<=n;j++)	
		if(s[i]+a[j]>s[i])
			s[i]=s[i]+a[j];
		else
			y=j-1;
		if(s[i]-1>=max)
			max=s[i]-1;

	}
h<<max;

return 0;}