도시 건설(백준 21924)

import sys
import heapq 
input= sys.stdin.readline
n,m= map(int, input().split())
gra=[[]for _ in range(n+1)]
visit= [0 for _ in range(n+1)]
total = 0 
ans =0 

for i in range(m):
    a,b,c = map(int, input().split())
    total += c 
    gra[a].append((b,c))
    gra[b].append((a,c))

def prim(start):
    global ans 
    q = [[0,start]]
    heapq.heapify(q)
    while q :
        cost, now =heapq.heappop(q)
        if visit[now] ==0:
            visit[now] = 1 
            ans+= cost 
            for nextnode, nextcost in gra[now]:
                if visit[nextnode] ==0 :
                    heapq.heappush(q,(nextcost,nextnode))
                    
prim(1)

print(total-ans if (0 not in visit[1:]) else -1)