#include <iostream>
#include <cstdio>
#include <string>
using namespace std;
#define E 10000000000
typedef long long int ll;
int main(){
	int n;	cin>>n;
	string a;
	ll sei=0,syo=0;
	for(int i=0;i<n;i++){
		cin>>a;
		ll tsei=0,tsyo=0;
		int syocnt=0;
		bool plus=true,seisyo=true;
		for(int j=0;j<(int)a.size();j++){
			if(a[j]=='.')	seisyo=false;
			else if(a[j]=='-')	plus=false;
			else{
				if(seisyo)	tsei=tsei*10+(ll)(a[j]-'0');
				else{
					tsyo=tsyo*10+(ll)(a[j]-'0');
					syocnt++;
				}
			}
		}
		for(int j=syocnt;j<10;j++)	tsyo*=10;
		if(plus){
			syo+=tsyo;	sei+=tsei+(syo/E);	syo%=E;
		}
		else{
			syo-=tsyo;
			if(syo<0){
				sei--;	syo+=E;
			}
			sei-=tsei;
		}
	}
	if(syo>0&&sei<0){
		sei++;
		syo-=E;
		syo*=-1;
	}
	printf("%lld.%010lld\n",sei,syo);
	return 0;
}