#include <iostream>
#include <fstream>
#include <cmath>

int main() {
	using namespace std;

	ifstream file("input.txt");
	ofstream outfile("output.txt");
	if (!file.is_open()) { cout << "file not found"; exit(1); }

	long long sum = 0;
	long long tmp = 0;
	long long am = 0;

	while (!file.eof()) {
		file >> tmp;
		sum += tmp;
		am++;
	};

	outfile << round(float(sum) / am * 1000) / 1000;
};