Code：

#include<queue>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn = 500000 + 555;
const int inf = -1223;
int ch[maxn][2], f[maxn], numv[maxn], maxv[maxn], lmax[maxn], rmax[maxn], sumv[maxn], tag[maxn], lazy[maxn], arr[maxn];
int  cnt,
 
 root, siz[maxn];
stack <int> S;
struct Operation
{
    inline int init(){ }
    void recycle(int u)
    {
        if(!u) return ;
        S.push(u);
        recycle(ch[u][0]); 
        recycle(ch[u][1]);
    }
    inline void pushup(int o)
    {
        int ls = ch[o][0], rs = ch[o][1];
        maxv[
 
o] = numv[o];
        siz[o] = siz[ls] + siz[rs] + 1;
        int sums = numv[o];
        if(ls) maxv[o] = max(maxv[o], maxv[ls]), sums += rmax[ls];
        if(rs) maxv[o] = max(maxv[o], maxv[rs]), sums += lmax[rs];
        maxv[o] = max(maxv[o], sums);
        lmax[o] = max(lmax[ls], sumv[ls] + numv[
 
o] + lmax[rs]);
        rmax[o] = max(rmax[rs], sumv[rs] + numv[o] + rmax[ls]);
    }
    inline void maintain(int o)
    {
        maxv[o] = max(numv[o], sumv[o]);
        lmax[o] = rmax[o] = max(0, sumv[o]);
    }
    inline void pushdown(int x,int l,int r)
    {
        int mid = (l + r) >> 1, ls = ch[x][0], rs = ch[x][1];
        if(lazy[x] != inf)
        {
            if(ls){ numv[ls] = lazy[ls] = lazy[x], sumv[ls] = (mid - l) * numv[ls]; maintain(ls); }
            if(rs){ numv[rs] = lazy[rs] = lazy[x], sumv[rs] = (r - mid) * numv[rs]; maintain(rs); }
            lazy[x] = inf;
        }
        if(tag[x])
        {
            swap(lmax[ls], rmax[ls]);  swap(lmax[rs], rmax[rs]);
            swap(ch[ls][0], ch[ls][1]);  swap(ch[rs][0], ch[rs][1]);
            if(ls) tag[ls] ^= 1;
            if(rs) tag[rs] ^= 1;
            tag[x] = 0;
        }
    }
}T;
void build(int l,int r,int fa,int o)
{
    if(l > r) return ;
    int mid = (l + r) >> 1;
    o = ++cnt;
    f[o] = fa, numv[o] = arr[mid];
    sumv[o] = sumv[ls] + sumv[rs] + numv[o];
    maintain(o);
    build(l, mid - 1, o, ch[o][0]);
    build(mid + 1, r, o, ch[o][1]);
    pushup(o);
}
inline void rotate(int x)
{
    int old = f[x], oldf = f[old], which = get(x);
    ch[old][which] = ch[x][which ^ 1], f[ch[old][which]] = old;
    ch[x][which ^ 1] = old, f[old] = x, f[x] = oldf;
    if(oldf) ch[oldf][ch[oldf][1] == old] = x;
    pushup(old); pushup(x);
}
inline void Splay(int x, int &tar)
{
    int a = f[tar];
    for(int fa; (fa = f[x]) != a; rotate(x));
        if(f[fa] != a) rotate(get(fa) == get(x) ? fa : x);
    tar = x;
}
inline void split(int &a , int nums , int &b)
{

}
int main(){


}