10pts求diao

#include <bits/stdc++.h>

#define un unsigned
#define rei register int//加速专用x7.0
#define ll  long long 
#define ris(x,y,z) for(un rei x=y;x<z+1;++x)
#define riso(x,y,a) for(un rei x=y;x;x=a)

using namespace std;

const ll N=6005;

struct edge{
    ll n,t,v;
}e[N];
ll h[N],cnt=0;
inline void add(ll u,ll v){
    e[++cnt].n=h[u];
    e[cnt].t=v;
    h[u]=cnt;
}

ll n,t,dp[N][2],a[N],p[N]={0};

void dfs(ll x){
    riso(i,h[x],e[i].n){
        ll v=e[i].t;
        dfs(v);
        dp[x][0]+=max(dp[v][1],dp[v][0]);
        dp[x][1]+=dp[v][0];
    }
    dp[x][1]+=h[x];
}

int main(){
    cin>>n;
    ris(i,1,n)
        cin>>a[i];
    ris(i,1,n-1){
        ll x,y;
        cin>>x>>y;
        ++p[x];
        if(x&&y)
            add(y,x);
    }
    ris(i,1,n-1)
        if(!p[i])
            t=i;
    dfs(t);
    cout<<max(dp[t][0],dp[t][1]);
    return 0;
}