def avg(*n):
    sumOfNumber = 0
    for t in n:
        sumOfNumber = sumOfNumber + t
    avge = sumOfNumber / len(n)
    return avge
if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')
    
    nums = list(map(int, input().split()))
    res = avg(*nums)
    
    fptr.write('%.2f' % res + '\n')

    fptr.close()