Problem:
Score : 100 points

Problem Statement

There is a tree with N vertices, numbered 1, 2, \ldots, N.
For each i (1 \leq i \leq N - 1), the i-th edge connects Vertex x_i and y_i.

Taro has decided to paint each vertex in white or black.
Here, it is not allowed to paint two adjacent vertices both in black.

Find the number of ways in which the vertices can be painted, modulo 10^9 + 7.

Constraints

All values in input are integers.

1 \leq N \leq 10^5

1 \leq x_i, y_i \leq N

The given graph is a tree.

Input

Input is given from Standard Input in the following format:

N
x_1 y_1
x_2 y_2
:
x_{N - 1} y_{N - 1}

Output

Print the number of ways in which the vertices can be painted, modulo 10^9 + 7.

Sample Input 1

3
1 2
2 3

Sample Output 1

5

There are five ways to paint the vertices, as follows:

Sample Input 2

4
1 2
1 3
1 4

Sample Output 2

9

There are nine ways to paint the vertices, as follows:

Sample Input 3

1

Sample Output 3

2

Sample Input 4

10
8 5
10 8
6 5
1 5
4 8
2 10
3 6
9 2
1 7

Sample Output 4

157

Solution in Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
import java.lang.*;
import java.io.*;
public class Main
{
    static FastScanner sc = new FastScanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static int mod=(int)1e9+7;
    static int dp[][]=new int[100005][2];
    static ArrayList<Integer> edges[] = new ArrayList[100005];
    
    public static void dfs(int node ,int parent ){
        dp[node][0]=1;
        dp[node][1]=1;

        for(int i=0;i<edges[node].size();i++){
            int to= edges[node].get(i);
            if(to==parent) continue;
            dfs(to,node);
            dp[node][0]=(dp[node][0]*((dp[to][0]+dp[to][1])%mod))%mod;
            dp[node][1]=(dp[node][1]*dp[to][0])%mod;
        }
    }
    public static void main(String args[]) throws Exception
    {
        int n=sc.nextInt();

        for(int i=0;i<n+1;i++){
            edges[i]=new ArrayList<>();
        }

        for(int i=0;i<n-1;i++){
            int u=sc.nextInt();
            int v=sc.nextInt();
            edges[u].add(v);
            edges[v].add(u);
        }
        
        dfs(1,-1);
        // for(int i=1;i<n+1;i++){
        //     out.println(Arrays.toString(dp[i]));
        // }
        out.println((dp[1][0]+dp[1][1])%mod);

        out.close();
    }


}
class FastScanner
{

    final private int BUFFER_SIZE = 1 << 17;
    private DataInputStream din;
    private byte[] buffer;
    private int bufferPointer, bytesRead;

    public FastScanner(InputStream in)
    {
        din = new DataInputStream(in);
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }
    public String nextLine() throws Exception
    {
        StringBuffer sb = new StringBuffer("");
        byte c = read();
        while (c <= ' ') c = read();
        do
        {
            sb.append((char)c);
            c = read();
        }
        while(c > ' ');
        return sb.toString();
    }

    public char nextChar() throws Exception
    {
        byte c = read();
        while(c <= ' ') c = read();
        return (char)c;
    }

    public int nextInt() throws Exception
    {
        int ret = 0;
        byte c = read();
        while (c <= ' ') c = read();
        boolean neg = c == '-';
        if (neg) c = read();
        do
        {
            ret = ret * 10 + c - '0';
            c = read();
        }
        while (c > ' ');
        if (neg) return -ret;
        return ret;
    }

    public long nextLong() throws Exception
    {
        long ret = 0;
        byte c = read();
        while (c <= ' ') c = read();
        boolean neg = c == '-';
        if (neg) c = read();
        do
        {
            ret = ret * 10 + c - '0';
            c = read();
        }
        while (c > ' ');
        if (neg) return -ret;
        return ret;
    }

    private void fillBuffer() throws Exception
    {
        bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
        if (bytesRead == -1) buffer[0] = -1;
    }

    private byte read() throws Exception
    {
        if (bufferPointer == bytesRead) fillBuffer();
        return buffer[bufferPointer++];
    }
    public double nextDouble() throws Exception
    {
        double ret = 0, div = 1;
        byte c = read();
        while (c <= ' ')
            c = read();
        boolean neg = (c == '-');
        if (neg)
            c = read();

        do
        {
            ret = ret * 10 + c - '0';
        }
        while ((c = read()) >= '0' && c <= '9');

        if (c == '.')
        {
            while ((c = read()) >= '0' && c <= '9')
            {
                ret += (c - '0') / (div *= 10);
            }
        }

        if (neg)
            return -ret;
        return ret;
    }


}