import sys


def main(argv=None):
    if argv is None:
        argv = sys.argv

    gamma_code = str(argv[1])

    N = gamma_code.index('1')
    M = int(gamma_code[-N:], 2)

    print(2**N + M)
    return 0


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