import re
import os
import sys


oldbim   = open(sys.argv[1])
newbim   = open(sys.argv[2])
newest   = open(sys.argv[3],"w")



for x in newbim:
    data = x.split()
    chr = data[0]
    snp = data[1]
    bp  = data[3]
    pos["%s-%s"%(chr,bp)]=snp

for y in newbim:
    data = x.split()
    chr = data[0]
    snp = data[1]
    bp  = data[3]
    hash = "%s-%s"%(chr,bp)
    pos[hash]=snp
    newsnp = pos.get(hash,"")
    if newsnp:
        if "rs" in snp and newsnp != snp:
            sys.exit("Mismatch on pos: old  %s  new %s "%(snp,newsnp)
        data[1]=newsnp
    newest.write("%s\n"%string.join(data,sep="\t"))
newest.close()