#include<iostream>
#include<string>
#include<cstdlib>
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;
        totaltask+=t;
    }
};
     void display()
{
    cout<<(float)e.totaltask/e.totalhours;
}
int main()
{
    employee e;
    e.setdata();
    employee::display(e);
    return 0;
    
    
}