#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
ll MOD = 1e9;
int charsearch(string s,char c){
    //文字cが文字列sに含まれるかどうか
    rep(i, 0, s.length()){
        if(s[i] == c)return i;
    }
    return -1;
}
main(){
    int sign = 1;
    ll num[2] = {};
    int N;
    cin >> N;
    rep(i,0,N){
        string s;
        cin >> s;
        int ind = charsearch(s,'.');
        ll a,b;
        if(ind != -1){
            //cout << s.substr(0,ind) << endl;
            //cout << s.substr(ind+1) << endl;
            a = stoll(s.substr(0,ind));
            b = stoll(s.substr(ind+1) + string(9 - (s.size() - ind - 1), '0') );
            //cout << a << " " << b << endl;  
        }else{
            a = stoll(s);
            b = 0;
        }
        int sign2 = s[0] == '-' ? -1 : 1;
        a = abs(a);
        if(sign == sign2){
            num[1] += b;
            num[0] += a + (num[1] / MOD);
            num[1] %= MOD;
        }else{
            if(num[0] < a || num[0] == a && num[1] < b){
                swap(num[0], a);
                swap(num[1], b);
                sign = sign2;
            }
            num[1] -= b;
            if(num[1] < 0){
                num[0]--;
                num[1] += MOD;
            }
            num[0] -= a;
        }
    }
    num[0] *= sign;
    printf("%lld.%010lld", num[0], num[1]);
}