#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
    string userType,userId,goal;
    int logs;
    cin>> userType>>userId;
    cin>>goal>>logs;
    double totalDuration= 0, totalCalories = 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;
        totalClories +=calores;
        
    }
    double average = totalCalories / totalDuration;
    cout << fixed <<setprecison(2)<<average;
    return 0
    
}