#include<cstdio>

#include<iostream>

#include<algorithm>

#include<cstring>

#define R register int

using namespace std;

#define ull unsigned long long

#define ll long long

#define pause (for(R i=1;i<=10000000000;++i))

#define IN freopen("NOIPAK++.in","r",stdin)

#define OUT freopen("out.out","w",stdout)

namespace Fread {

    static char B[<<],*S=B,*D=B;

#ifndef JACK

    #define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)

#endif

    inline int g() {

        R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

        if(ch==EOF) return EOF; do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

    } inline bool isempty(const char& ch) {return (ch<=||ch>=);}

    inline void gs(char* s) {

        register char ch; while(isempty(ch=getchar()));

        do *s++=ch; while(!isempty(ch=getchar()));

    }

}using Fread::g; using Fread::gs;

const int N=,B=;

int ch[N][];

#define ls ch[u][0]

#define rs ch[u][1]

int n,w[N],sz[N],d[N],ans,mxd;

ull h1[N],h2[N],p[N],tmp;

inline void dfs1(int u) { mxd=max(d[u],mxd);

    if(~ls) d[ls]=d[u]+,dfs1(ls); if(~rs) d[rs]=d[u]+,dfs1(rs);

}

inline void dfs(int u) {sz[u]=;

    if(~ls) dfs(ls),sz[u]+=sz[ls]; if(~rs) dfs(rs),sz[u]+=sz[rs];

    if(~ls&&~rs&&sz[ls]==sz[rs]&&h1[ls]==h2[rs]&&h2[ls]==h1[rs]) ans=max(ans,sz[u]);

    if(!~ls&&!~rs) h1[u]=h2[u]=w[u],ans=max(ans,); else if(~ls&&!~rs) h1[u]=h1[ls]*p[d[u]]+w[u]*(p[d[u]]-),h2[u]=h2[ls]+w[u]*(p[d[u]]-);

    else if(!~ls&&~rs) h1[u]=w[u]*(p[d[u]]-)+h1[rs],h2[u]=w[u]*(p[d[u]]-)+h2[rs]*p[d[u]];

    else h1[u]=h1[ls]*p[d[u]]+w[u]*(p[d[u]]-)+h1[rs],h2[u]=h2[ls]+w[u]*(p[d[u]]-)+h2[rs]*p[d[u]];

}

signed main() {

#ifdef JACK

IN;

#endif

    n=g(); for(R i=;i<=n;++i) w[i]=g(); for(R u=;u<=n;++u) ls=g(),rs=g();

    d[]=; dfs1();

    for(R i=;i<=n;++i) d[i]=mxd-d[i]; p[]=; tmp=p[]=B; for(R i=;i<=mxd;++i) p[i+]=(tmp*=tmp);

    dfs(); printf("%d\n",ans);

}