#include<iostream>
using namespace std;

int main(){
    int n;
    float grade,sum=0;
    
    if(!(cin>>n)) return 0;
    
    for(int i=0;i<n;i++){
        cin>>grade;
        if(grade<0){
            cout<<"Invalid Input"<<endl;
            return 0;
        }
        sum+=grade;
    }
    cout<<sum/n<<end;
    return 0;
}