N,M = map(int, input().split())

V = [0] * N
for _ in range(M):
    u,v,w = map(int,input().split())
    u = u-1
    v = v-1
    V[u] = V[u] + w
    V[v] = V[v] + w

V.sort(reverse=True)

ans = 0
for i in range(N):
    if i%2:
        ans -= V[i]
    else:
        ans += V[i]

print(ans//2)