N, M = map(int, input().split()) D = [[float('inf')] * N for _ in range(N)] for i in range(N): D[i][i] = 0 for _ in range(M): s, t, d = map(int, input().split()) D[s-1][t-1] = min(D[s-1][t-1], d) for k in range(N): for i in range(N): for j in range(N): D[i][j] = min(D[i][j], D[i][k] + D[k][j]) for i in range(N): s = 0 for j in range(N): if D[i][j] != float('inf'): s += D[i][j] print(s)