import rdflib
import json
import argparse


ap = argparse.ArgumentParser("")
ap.add_argument("input", nargs="+")
args = ap.parse_args()

context = None
u = rdflib.Graph()
for i in args.input:
    if context is None:
        with open(i) as fin:
            data = json.load(fin)
        if '@context' in data:
            context = data['@context']
    g = rdflib.Graph()
    g.parse(i)
    u += g

print (u.serialize(format="json-ld", context=context))