#include <iostream>
#include <stdio. h>
using namespace std;
int main()
{
int sum=0,n,count=1, count_ch=0;
float result;
cin >> n;
if (n<10000)
{
while (n != 0)
{
if (n % 2 == 0)
{
sum += n;
count_ch++;
}
cin >> n;
count++;
if (n > 10000 or count > 1000)
{
break;
}
}
}
result = sum/count_ch;
printf("%. 2f",result);
}