#include<iostream>
using namespace std;

class Employee
{
    private:
    string name, id;
    int logs;
    int totalHours = 0, totalTask =0;
    
    public:
    void setData()
    {
        cin >> name >> id >> logs;
        if(logs < 1 || logs > 10)
        {
            cout << " Invalid input";
            exit(0);
            
        }
        for (int i = 0; i < logs; i++)
        {
            int h,t;
            cin >> h >> t;
            if (h < 1 || h > 24 || t < 0 || t > 100)
            {
                cout << " Invalid input";
                exit(0);
                
            }
            totalHours += h;
            totalTasks += t;
        }
    }
    static void display(Employee e)
    {
        cout << (float)e.totalTask / e.totalHours;
    }
};

int main()
{
    Employee e;
    e.setData();
    Employee::display(e);
    return 0;
}