bzoj2442

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=200005;
int n,m,a[N],p[N];
ll sum[N],q[N],f[N];
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)scanf("%d",&a[i]);
    for (int i=1;i<=n;i++)sum[i]=sum[i-1]+a[i];
    f[1]=a[1];p[2]=1;q[2]=-a[1];
    int l=1,r=2;
     for (int i=2;i<=n;i++)
     {
         if (p[l]+m<i)l++;
         f[i]=sum[i]+q[l];
         while (l<=r&&q[r]<=f[i-1]-sum[i])r--;
         p[++r]=i;q[r]=f[i-1]-sum[i];
     }
    printf("%lld",f[n]); 
}