def rerooting():  
  dp=[[E]*len(edge[v]) for v in range(n)]
  
  # dfs1
  memo=[E]*n
  for v in order[::-1]:
    res=E
    for i in range(len(edge[v])):
      if edge[v][i]==par[v]:
        continue
      dp[v][i]=memo[edge[v][i]]
      res=merge(res,f(dp[v][i],edge[v][i],v))
    memo[v]=g(res,v)
  
  # dfs2
  memo2=[E]*n
  for v in order:
    for i in range(len(edge[v])):
      if edge[v][i]==par[v]:
        dp[v][i]=memo2[v]
    
    s=len(edge[v])
    cumR=[E]*(s+1)
    cumR[s]=E
    for i in range(s,0,-1):
      cumR[i-1]=merge(cumR[i],f(dp[v][i-1],v,edge[v][i-1]))
      
    cumL=E
    for i in range(s):
      if edge[v][i]!=par[v]:
        val=val=merge(cumL,cumR[i+1])
        memo2[edge[v][i]]=g(val,v)
      cumL=merge(cumL,f(dp[v][i],edge[v][i],v))
  
  
  ans=[E for i in range(n)]

  for v in range(n):
    res=E
    for i in range(len(edge[v])):
      res=merge(res,f(dp[v][i],edge[v][i],v))
    ans[v]=g(res,v)
    #ans[v]=calc_ans(res,v)

  return ans



E=(0,0,0)
mod=10**9+7

def f(res,v,u):
  a,b,c=res
  w=weight[v+(u<<20)]
  a+=2*w*b+c*w%mod*w
  a%=mod
  b+=c*w
  b%=mod 
  return (a,b,c)
 
def g(res,v):
  a,b,c=res
  return (a,b,c+1)
 
def merge(a,b):
  xa,ya,za=a
  xb,yb,zb=b
  return ((xa+xb)%mod,(ya+yb)%mod,za+zb)

'''
def calc_ans(res,v):
  return
'''


from sys import stdin
input=lambda :stdin.readline()[:-1]


weight={}
n=int(input())
edge=[[] for i in range(n)]
for i in range(n-1):
  x,y,w=map(int,input().split())
  x,y=x-1,y-1
  edge[x].append(y)
  edge[y].append(x)
  weight[x+(y<<20)]=w
  weight[y+(x<<20)]=w


# make order table
# root = 0

from collections import deque
order=[]
par=[-1]*n
todo=deque([0])
while todo:
  v=todo.popleft()
  order.append(v)
  for u in edge[v]:
    if u!=par[v]:
      par[u]=v
      todo.append(u)

ans=rerooting()
res=0
for i in ans:
  res+=i[0]

res%=mod
res*=pow(2,mod-2,mod)
print(res%mod)