import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Scanner;
class Ideone
{
{
double salary, totalSalary=0, employeesNum=0;
Scanner in
= new Scanner
(System.
in);
while (in.hasNext())
{
name = in.next();
salary = in.nextDouble();
totalSalary+=salary;
employeesNum++;
}
System.
out.
println(totalSalary
/employeesNum
); }
}
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