~能过~

#include <stdio.h>
#include <stdlib.h>

#define MAX(a,b) (a>b?a:b)

int main() {
	int n, m, max=0, head=0, tail=0;
	int i,j;
	scanf("%d%d",&n,&m);
	
	int *sum = (int*)calloc(n+1, sizeof(int));
	int *temp = (int*)calloc(n+1, sizeof(int));
	
	temp[tail++] = 0;
	 
	//输入数组，改造为前缀和数组
	for(i=1; i<=n; i++) {
		scanf("%d",&sum[i]);
		sum[i] += sum[i-1];
	}
	
	for(i=1; i<=n; i++) {
		j = sum[i]-sum[temp[head]]; //求区间和
		max = MAX(max,j);           //比较
		while(tail-head && sum[i]<sum[temp[tail-1]]) tail--;
		temp[tail++] = i;
		if(i - temp[head] == m) head++; //子序列超过范围，最小值过期
	}
	
	printf("%d",max);
	return 0;
}