#!/usr/bin/env python

import os.path
import site
import sys


def main():
    """
    Check if the given prefix is included in sys.path for the given
    python version; if not find an alternate valid prefix.  Print the
    result to standard out.
    """
    if len(sys.argv) != 3:
        msg = "usage: %s <prefix> <python version>\n" % os.path.basename(sys.argv[0])
        sys.stderr.write(msg)
        return 1
    python_prefix = sys.argv[1]
    python_version = sys.argv[2]
    path = "%s/lib/python%s" % (python_prefix, python_version)
    path = os.path.normpath(path)
    if path[-1] != "/":
        path += "/"
    prefix = None
    for p in sys.path:
        if p.startswith(path):
            prefix = python_prefix
            break
    if not prefix:
        prefix = site.PREFIXES[-1]
    sys.stdout.write("%s\n" % prefix)
    return 0


if __name__ == "__main__":
    sys.exit(main())