import java.io.BufferedReader;
import java.io.FileReader;

public class Scorecal {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new FileReader("C:\\Users\\黄志楷\\Documents\\ocix\\学校相关\\jwork\\w7\\score"));
        String line;
        int sum = 0;
        int count = 0;
        while ((line = br.readLine()) != null) {
            sum += Integer.parseInt(line);
            count++;
        }
        br.close();
        System.out.println((double) sum / count);
    }
}