root = {}
root['a'] = {'b':2, 'c':2}
root['b'] = {'goal': 3}
root['c'] = {'d':1}
root['d'] = {'goal':1}


# a - b  -goal
# 0 2 3 sum 5
# a - c - d goal
# 0 2 1 1 sum 4

for k1, v1 in root['a'].items():
    l1 = 0 + v1
    for k2, v2 in root[k1].items():
        l2 = l1 + v2
        if 'goal' == k2:
            print("{} - {} - {} ({})".format('a', k1,k2, l2))
            break
        for k3, v3 in root[k2].items():
            l3 = l2 + v3
            print("{} - {} - {} - {} ({})".format('a', k1,k2,k3, l3))