#!/usr/bin/python

import sys
import ra


def union(theOne, theOther):
    if not theOne.unionCompatible(theOther):
        raise TypeError, "%s is not union compatible with previous input." % a
    answer = ra.Relation()
    answer.attributes = theOne.attributes
    answer.data = theOne.data.union(theOther.data)
    return answer

def newRelationFromFile(theFileName):
    f = None
    if "-" == theFileName:
        f = sys.stdin
    else:
        f = open(theFileName)
    return ra.newRelationFromTSV(f)

if __name__ == "__main__":
    answer = ra.Relation()

    if len(sys.argv) < 2:
        answer = newRelationFromTSV(sys.stdin)
    else:
        answer = newRelationFromFile(sys.argv[1])
        for a in sys.argv[2:]:
            r = newRelationFromFile(a)
            answer = union(answer, r)
    answer.toTSV()