n, m = map(int, input().split())

g = [[float("inf") for i in range(n+1)] for i in range(n+1)]
st = [False for i in range(n+1)]
dist = [float("inf") for i in range(n+1)]

for _ in range(m):
    a, b, w = map(int, input().split())
    g[a][b] = min(g[a][b], w)
    g[b][a] = min(g[b][a], w)

def prim():
    ans = 0
    for i in range(n):
        t = -1
        for j in range(1,n+1):
            if st[j] == False and (t == -1 or dist[j] < dist[t]):t = j
        if i != 0 and dist[t] == float("inf"):return "impossible"
        st[t] = True
        if i != 0:ans += dist[t]
        for j in range(1, n+1):dist[j] = min(dist[j], g[t][j])
    return ans

print(prim())