防守阵地 I

#include<stdio.h>
#include<string.h>
int sum[1000005],s[1000005];
int main()
{
  int n,m,i,x,max;
  while(scanf("%d%d",&n,&m)!=EOF)
  {
      max=0;
     memset(sum,0,sizeof(sum));
     memset(s,0,sizeof(s));
     sum[0]=s[0]=0;
     for(i=1;i<=n;i++)
      {
      scanf("%d",&x);
      sum[i]=sum[i-1]+x;
      s[i]=s[i-1]+sum[i]; 
      }            
      
       if(n<m) {printf("%d\n",s[n]);continue;}
       for(i=m;i<=n;i++)
       {
         int ans=m*sum[i]-s[i-1]+s[i-m-1];
         if(ans>max) max=ans;                 
       }          
       printf("%d\n",max);
  }
return 0;
}