from sys import stdin
input = stdin.readline

N, M = map(int, input().split())
edge = [list(map(int, input().split())) for _ in range(M)]

score = [0]*N
for u, v, w in edge:
    u, v = u-1, v-1
    score[u] += w
    score[v] += w

score.sort(reverse=True)

alice = 0
bob = 0
for i in range(N):
    if i%2 == 0:
        alice += score[i]
    else:
        bob += score[i]

print((alice-bob)//2)