def main():
    n, m = list(map(int, input().split()))
    X = [0] * n
    for _ in range(m):
        u, v, w = list(map(lambda x: int(x)-1, input().split()))
        X[u] += w+1
        X[v] += w+1
    X.sort()
    ans = 0
    for i in range(1, n+1):
        ans += X[-i] if i % 2 else -X[-i]
    return ans//2

print(main())