##################################
#                                #
# Last modified 01/10/2009       # 
#                                #
# Georgi Marinov                 #
#                                # 
##################################

import sys

try:
	import psyco
	psyco.full()
except:
	pass

def run():

    if len(sys.argv) < 3:
        print 'usage: python %s inputfilename outfilename trim-to-bp' % sys.argv[0]
        sys.exit(1)

    inputfilename = sys.argv[1]
    outputfilename = sys.argv[2]
    newlength = int(sys.argv[3])

    outfile = open(outputfilename, 'w')

    listoflines = open(inputfilename)
    i=0
    for line in listoflines:
        if i % 1000000 == 0:
            print i, 'reads processed'
        i+=1
        fields = line.strip().split('\t')
        outfile.write(fields[0])
        outfile.write('\n')
        outfile.write(fields[1][0:newlength])
        outfile.write('\n')

    outfile.close()

run()