import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
    
    public static int setLeafHeight(int element, int[] parentTree){
        if(parentTree[element] == 0){
            return 0;
        }
        return setLeafHeight(parentTree[element], parentTree) + 1;
        
    }
          
    
    public static int[] findHeights(ArrayList<Integer>[] tree, int[] parentTree){
        int[] heights = new int[tree.length];
        
        for(int i=tree.length-1; i>0; i--){
            if(i==1){
                heights[i] = 0;
            }
            else if(tree[i].size() ==0){
                heights[i] = setLeafHeight(i, parentTree);
            }
            else{
                int max = 0;
                for(int j=0; j<tree[i].size(); j++){
                    if(heights[tree[i].get(j)]>max){
                        max = heights[tree[i].get(j)];
                    }
                }
                heights[i] = max-1;
            }
        }
        
        return heights;        
    }
    
    public static int findSize(int element, ArrayList<Integer>[] tree){
        int size = 1;
        
        if(tree[element].size() == 0){
            size = 1;
        }
        
        else{
            for(int i=0; i<tree[element].size(); i++){
                size += findSize(tree[element].get(i), tree);
            }
            
        } 
        
        return size;
        
    }
    
    public static int[] findTreeSize(ArrayList<Integer>[] tree){
        int[] sizes = new int[tree.length];
        for(int i=tree.length-1; i>0; i--){
            
            
            if(tree[i].size()==0){
                sizes[i] = 1;
            } else {
                sizes[i] = findSize(i, tree);
            }
        }
        return sizes;
    }
    

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        ArrayList<Integer> tree[]=new ArrayList[n+1];
        int[] parentTree = new int[n+1];
        
        for(int i=1; i<=n; i++){
            tree[i] = new ArrayList<Integer>();
        }
        
        
        for(int a0 = 0; a0 < n-1; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            
            tree[x].add(y);  
            parentTree[y] = x;
        }
               
        
        int[] heights = findHeights(tree, parentTree);
        int[] sizes = findTreeSize(tree);
        
        
        int sumOfHeights = 0;
        for (int j = 1; j<heights.length; j++){
            sumOfHeights += heights[j];
        }        
        
        double treeLost = 0;
        for(int k=1; k<tree.length; k++){
            for (int l=0; l<tree[k].size(); l++){
            
            treeLost += ((heights[tree[k].get(l)])/(double)sumOfHeights)*sizes[tree[k].get(l)];

            }
        }
        
        double treeLeft = ((double)n-treeLost);
        
        System.out.println(treeLeft);
        

        in.close();
    }
}