#include<iostream>
#include<string>
#include<iomanip>
using namespace std;
class tracker
{
    private:
    string name;
    string id;
    int logs;
    public:
    void sname(string n)
    {
        name=n;
    }
    void slogs(int l)
    {
        logs=1;
    }
    string getName()const
    {
        return name;
    }
    string getId()const
    {
        return id;
    }
    int getLogs()const
    {
        return logs;
    }
    static void calcndis()
    {
        string n,i;
        int l;
        cin>>n>>i>>l;
        if(l<1||l>10)
        {
            cout<<"Invalid input"<<endl;
            return;
        }
        double tothours=0;
        double tottasks=0;
        bool valid = true;
        for(int k =0; k<1; ++k)
        {
            int hours, tasks;
            cin>>hours>>tasks;
        }
        if(hours<1||hours>24||tasks<0||task>100)
        {
            valid=false;
        }
        tothours+=hours;
        tottasks+=tasks;
    }
    if(!valid)
    {
        cout<<"Invalid input"<<endl;
    }
    else if(tothours==0)
    {
        cout<<0.0<<endl;
    }
    else
    {
        double average=tottasks/tothours;
        cout<<fixed<<setprecision(2)<<average>>endl;
    }
};
int main()
{
    tracker::calcndis();
    return 0;
}