最大子序列和

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <climits>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <vector>
#include <list>
#include <bitset>
#define rep(i,m,n) for(i=m;i<=n;i++)
#define rsp(it,s) for(set<int>::iterator it=s.begin();it!=s.end();it++)
#define vi vector<int>
#define pii pair<int,int>
#define mod 1000000007
#define inf 0x3f3f3f3f
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
#define pi acos(-1.0)
const int maxn=1e6+10;
const int dis[4][2]={{0,1},{-1,0},{0,-1},{1,0}};
using namespace std;
ll gcd(ll p,ll q){return q==0?p:gcd(q,p%q);}
ll qpow(ll p,ll q){ll f=1;while(q){if(q&1)f=f*p;p=p*p;q>>=1;}return f;}
int n,m,a[maxn];
ll sum[maxn],ma;
void update(int p,int q)
{
    p+=n-1;
    a[p]=q;
    while(p)
    {
        p=(p-1)/2;
        a[p]=min(a[2*p+1],a[2*p+2]);
    }
}
int query(int ql,int qr,int p,int l,int r)
{
    if(r<=ql||qr<=l)return inf;
    else if(ql<=l&&r<=qr)return a[p];
    else return min(query(ql,qr,p*2+1,l,(l+r)/2),query(ql,qr,p*2+2,(l+r)/2,r));
}
int main()
{
    int i,j,k,t;
    memset(a,inf,sizeof(a));
    scanf("%d",&t);
    n=1;
    while(n<t)n<<=1;
    rep(i,0,t-1)
    {
        scanf("%d",&j);
        if(i)sum[i]=sum[i-1]+j;
        else sum[i]=j;
        update(i,sum[i]);
    }
    scanf("%d",&m);
    ma=sum[0];
    rep(i,1,t-1)
    {
        ma=max(ma,sum[i]-query(max(i-m,0),i,0,0,n));
    }
    printf("%lld\n",ma);
    //system ("pause");
    return 0;
}