void plusMinus(vector<int> arr) {
    double sp, sn, sz, pa = 1.0 / arr.size();
    sp = sn = sz = 0;
    for(int i = 0; i < arr.size(); i++){
        if(arr[i] > 0) sp+= pa;
        else if(arr[i]<0) sn+= pa;
        else sz+= pa;
    }
    cout << setprecision(6) << fixed;
    cout << sp <<endl;
    cout << sn <<endl;
    cout << sz <<endl;
}