import time as t
def stopwatch(sec):
    while sec:
        minn, secc = divmod(sec, 60)
        timeformat = '{:02d}:{:02d}'.format(minn, secc)
        print(timeformat, end='\r')
        t.sleep(1)
        sec -= 1
    
print('Goodbye!\n')   
stopwatch(15)
