#!/usr/bin/python
import sys
import os
import glob
import time

if len(sys.argv) == 2 and sys.argv[1] == '1820':
    os.system('modprobe w1-gpio')
    os.system('modprobe w1-therm')
    base_dir = '/sys/bus/w1/devices/'
    device_folder = glob.glob(base_dir + '28*')[0]
    device_file = device_folder + '/w1_slave'
else:
    sys.exit(1)


def read_temp_raw():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines


def read_temp():
    lines = read_temp_raw()
    while lines[0].strip()[-3:] != 'YES':
        time.sleep(0.2)
        lines = read_temp_raw()
    equals_pos = lines[1].find('t=')
    if equals_pos != -1:
        temp_string = lines[1][equals_pos+2:]
        temp_c = float(temp_string) / 1000.0
        return temp_c

temperature = read_temp()
print '{0:0.1f}'.format(temperature)
sys.exit(1)