#include <iostream>
#include <iomanip>

int main() {
    int score1, score2, score3;
    std::cin >> score1 >> score2 >> score3;
    double average = static_cast<double>(score1 + score2 + score3) / 3;
    std::cout << std::fixed << std::setprecision(3) << average << std::endl;
    return 0;
}    
/**************************************************************
	Problem: 1957
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/