import math
input_line = input()
input_line_lst = input_line.split()
input_line_lst2 = [float(p) for p in input_line_lst]
result = sum(input_line_lst2) / len(input_line_lst2)
print(result)
aW1wb3J0IG1hdGgKaW5wdXRfbGluZSA9IGlucHV0KCkKaW5wdXRfbGluZV9sc3QgPSBpbnB1dF9saW5lLnNwbGl0KCkKaW5wdXRfbGluZV9sc3QyID0gW2Zsb2F0KHApIGZvciBwIGluIGlucHV0X2xpbmVfbHN0XQpyZXN1bHQgPSBzdW0oaW5wdXRfbGluZV9sc3QyKSAvIGxlbihpbnB1dF9saW5lX2xzdDIpCnByaW50KHJlc3VsdCk=