#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    string name,id;
    cin>>name>>id;
    int num;
    cin>>num;
    if(num>0 || num<=10){
        float hr[num],tk[num],s1=0,s2=0;
        float tot=0;
        for(int i=0;i<num;i++){
            cin>>hr[i]>>tk[i];
            if(hr[i]>=0 && hr[i]<=24&& tk[i]>=0&& tk[i]<=100){
                s1+=hr[i];
                s2+=tk[i];
            }
            else{
                cout<<"Invalid input";
                return 0;
            }
        }
        tot=s2/s1;
        cout<<fixed<<set precision(2)<<tot;
    }
    else{
        cout<<"Invalid input";
    }
}