#include <iostream>

using namespace std;

int main()
{
    int numbers;
    int wynik[100000];
    int k = 0;
    for(;;){
        cin >> numbers;
        wynik[k] = numbers;
        if(numbers == 0){
            wynik[k] = -1;
            break;
        }
        int numbs[numbers];
        int good[numbers];
        int bad[numbers];
        int nice = 0;
        int notnice = 0;
        for(int i = 0; i < numbers; i++){
            cin >> numbs[i];
            if(numbs[i] >= 0){
                good[i] = numbs[i];
                nice++;
            }
            else{
                bad[i] = numbs[i]*(-1);
                notnice++;
            }
        }
        for(int i = 0; i < notnice; i++){
            for(int c = 0; c <= nice; c++){
                if(bad[i] == good[c]){
                    wynik[k]--;
                    break;
                }
            }
        }
        if(nice == 0){
            wynik[k] = 0;
        }
        k++;
    }
    for(int z = 0; z <= k; z++){
        if(wynik[z] == -1) break;
        cout << wynik[z] << endl;
    }

    return 0;
}