#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    string usertype ,userID,goal;
    int logs;
    cin >> usertype >> userID;
    cin >> goal >> logs;
    double totalcalories =0,totalduration =0;
    for(int i=0 ;i<logs;i++){
        double duration ,calories;
        cin >> duration >> calories;
            if(duration <=0 ||calories<=0){
                cout <<"Invalid input";
                return 0;
            }
            totalduration += duration;
            totalcalories += calories;
        }
        double avg totalcalories / totalduration;
        cout << fixed <<setprecision(2) << avg;
        return 0;
    }