class USD():
    def __init__(self,N=10010):
        self.lt = [i for i in range(N+1)]

    def find(self, a):
        lt = self.lt
        if lt[a] !=a:
            lt[a] = self.find(lt[a])
        return lt[a]

    def merge(self,a,b):
        self.lt[self.find(a)] = self.find(b)


n,m = map(int,input().split(' '))
edges = []
for _ in range(m):
    a,b,c = map(int,input().split(' '))
    edges.append([c,a,b])

edges.sort()
usd = USD(n)
st = [False] * (n+1) 
w = 0
cnt = 0
for c,a,b in edges:
    if usd.find(a) != usd.find(b):
        w += c
        st[a] = st[b] = True
        cnt += 1
        usd.merge(a,b)
print(w) if cnt >= n-1 else print('impossible')