from atcoder.dsu import DSU
n,m=map(int,input().split())
que=[]
for _ in range(m):
    a,b,c=map(int,input().split())
    a-=1
    b-=1
    que.append((c,a,b))
que.sort(reverse=True)
uf=DSU(n)
ans=0
for i in range(m):
    d,a,b=que[i]
    if not uf.same(a,b):
        uf.merge(a,b)
        ans+=d
print(ans*2)