#include<iostream>
#include<iomanip>
#include<vector>
using namespace std;
class RainfallTracker{
    private:
    static double totalrainfall;
    public:
    static void addrainfall(double amount){
        totalrainfall+=amount;
    }
    static double getTotal(){
        return totalrainfall;
        
    }
    
};
double RainfallTracker::totalrainfall =0.0;
int main()
{
    int n;
    if(!(cin>>n)){
        return 0;
    }
    double currentrainfall;
    for (int i=0;i<n;++i){
        if(!(cin >> currentrainfall)){
            cout<<"incomplete data"<<endl;
            return 0;
    
        }
        if(currentrainfall<0){
            cout<<"invalid rainfall"<<endl;
            return 0;
        }
    RainfallTracker::addrainfall(currentrainfall);
        
    }
    cout<<fixed<<setprecision(2)<<rainfalltracker::getTotal()<<endl;
    return 0;
    
}