class UnionFind:
    def __init__(self, n):
        self.parent = list(range(n + 1))
        self.rank = [0] * (n + 1)

    def find(self, x):
        if self.parent[x] != x:
            self.parent[x] = self.find(self.parent[x])
        return self.parent[x]

    def union(self, x, y):
        root_x = self.find(x)
        root_y = self.find(y)
        if root_x != root_y:
            if self.rank[root_x] > self.rank[root_y]:
                self.parent[root_y] = root_x
            elif self.rank[root_x] < self.rank[root_y]:
                self.parent[root_x] = root_y
            else:
                self.parent[root_y] = root_x
                self.rank[root_x] += 1
    
    def same(self, x, y):
        return self.find(x) == self.find(y)

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(reverse=True)

uf = UnionFind(N)
ans = 0
for c, a, b in edges:
    if not uf.same(a, b):
        uf.union(a, b)
        ans += c

print(ans*2)