#include <iostream>
 
int average(int* total, int* count);
 
int main()
{
    int total[1];
    int temp[1];
    int count[1];
    *total = 0;
    *count = 0;
    std::cin >> *temp;
    while (*temp >= 0)
    {
        *total += *temp;
        ++(*count);
        std::cin >> *temp;
    }
    std::cout << average(total, count) << std::endl;
    return 0;
}
 
int average(int* total, int* count)
{
    if (*count != 0)
    {
        return (*total)/(*count);
    }
    return 0;
}

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Mgo0CjYKOAoxMAotMQo=

2
4
6
8
10
-1