n, m = map(int, input().split())
g = [0] * n
for _ in range(m):
    u, v, w = map(int, input().split())
    g[u-1] += w
    g[v-1] += w
g.sort(reverse=True)
ans = (sum(g[0::2]) - sum(g[1::2])) // 2
print(ans)