Mitya has a rooted tree with n vertices indexed from 1 to n, where the root has index 1. Each vertex v initially had an integer number a_v ≥ 0 written on it. For every vertex v Mitya has computed s_v: the sum of all values written on the vertices on the path from vertex v to the root, as well as h_v — the depth of vertex v, which denotes the number of vertices on the path from vertex v to the root. Clearly, s_1=a_1 and h_1=1.

Then Mitya erased all numbers a_v, and by accident he also erased all values s_v for vertices with even depth (vertices with even h_v). Your task is to restore the values a_v for every vertex, or determine that Mitya made a mistake. In case there are multiple ways to restore the values, you're required to find one which minimizes the total sum of values a_v for all vertices in the tree.

Input

The first line contains one integer n — the number of vertices in the tree (2 ≤ n ≤ 10^5). The following line contains integers p_2, p_3, ... p_n, where p_i stands for the parent of vertex with index i in the tree (1 ≤ p_i < i). The last line contains integer values s_1, s_2, ..., s_n (-1 ≤ s_v ≤ 10^9), where erased values are replaced by -1.

Output

Output one integer — the minimum total sum of all values a_v in the original tree, or -1 if such tree does not exist.

Examples

Input


5
1 1 1 1
1 -1 -1 -1 -1


Output


1


Input


5
1 2 3 1
1 -1 2 -1 -1


Output


2


Input


3
1 2
2 -1 1


Output


-1
import java.util.*;
import java.io.*;
//import java.math.*;

public class Task{
        //  ..............code begins here..............

static long mod=(long)1e9+7;
static long res=0;
static int[] ss;
static void dfs(List<Integer>[] g, int s,int pp,long pre,int l){
    long min=2000000000;
    for(int c:g[s]){
        if(c!=pp){
            min=Math.min(min,ss[c-1]);
        }
    }
    if(l%2==1&&ss[s-1]-pre<0){
        res=-(long)1e15; return;
    }
    if(l%2==0&&pre>min){
        res=-(long)1e15; return;
    }
    if(l%2==1)res+=ss[s-1]-pre;
    else if(min!=2000000000){
        res+=min-pre;
    }
    for(int c:g[s]){
        if(c!=pp){
            if(l%2==1){
                dfs(g,c,s,ss[s-1],l+1);
            }
            else{
                dfs(g,c,s,min,l+1);
            }
        }
    }
}
static void solve() throws  IOException {
            int n=int_v(read());
            List<Integer>[] g=new ArrayList[n+1];
            for(int i=0;i<=n;i++) g[i]=new ArrayList<>();
            int[] a=int_arr();
            for(int i=0;i<n-1;i++){
               g[a[i]].add(i+2);
               g[i+2].add(a[i]);
            }
            ss=int_arr();
            dfs(g,1,-1,0,1);
            if(res<0) out.write("-1");
            else out.write(res+"\n");
}
   
public static void main(String[] args) throws  IOException{
                assign();
                int t=1;//int_v(read());
                while(t--!=0) solve();
                out.flush();
}

// taking inputs
static long pow1(long a,int p){long res=1;while(p>0){if((p&1)!=0){res=(res*a);}p >>=1;a=(a*a);}return res;}

static BufferedReader s1;
static BufferedWriter out;
static String read() throws IOException{String line="";while(line.length()==0){line=s1.readLine();continue;}return line;}
static int int_v (String s1){return Integer.parseInt(s1);}
static long long_v(String s1){return Long.parseLong(s1);}
static void sort(int[] a){List<Integer> l=new ArrayList<>();for(int x:a){l.add(x);}Collections.sort(l);for(int i=0;i<a.length;i++){a[i]=l.get(i);}}
static int[] int_arr() throws IOException{String[] a=read().split(" ");int[] b=new int[a.length];for(int i=0;i<a.length;i++){b[i]=int_v(a[i]);}return b;}
static long[] long_arr() throws IOException{String[] a=read().split(" ");long[] b=new long[a.length];for(int i=0;i<a.length;i++){b[i]=long_v(a[i]);}return b;}
static void assign(){s1=new BufferedReader(new InputStreamReader(System.in));out=new BufferedWriter(new OutputStreamWriter(System.out));}
//static String setpreciosion(double d,int k){BigDecimal d1 = new BigDecimal(Double.toString(d));return d1.setScale(k,RoundingMode.HALF_UP).toString();}//UP DOWN HALF_UP
static int gcd(int a,int b){if(b==0){return a;}return gcd(b,a%b);}
static long Modpow(long a,long p,long m){long res=1;while(p>0){if((p&1)!=0){res=(res*a)%m;}p >>=1;a=(a*a)%m;}return res%m;}
static long Modmul(long a,long b,long m){return ((a%m)*(b%m))%m;}
static long ModInv(long a,long m){return Modpow(a,m-2,m);}
//static long nck(int n,int r,long m){if(r>n){return 0l;}return Modmul(f[n],ModInv(Modmul(f[n-r],f[r],m),m),m);}
//static long[] f;
}