#include <iostream>
#include <string>
#include <vector>
#include <iomanip>
using namespace std;

int main(){
    string userType,userID,goal;
    int numlogs;
    
    if(!(cin>>userType>>userID))
    return 0;
    
    if(!(cin>>goal>>numlogs))
    return 0;
    
    double totalDuration =0;
    double totalCalories =0;
    bool hasError= false;
    for(int i=0; i<numlogs;i++){
        double d,c;
        cin>>d>>c;
        
        if(d<=0 || c<=0){
            hasError = true;
        }
        
        totalDuration +=d;
        totalCalories +=c;
    }
    if (hasError){
        cout<<"Invalid input"<<endl;
    }
    else{
        double average = totalCalories /totalDuration;
        cout<<fixed<<setprecision(2)<<average<<endl;
    }
}
return 0;
}