#include <fstream>

using namespace std;

ifstream cin("culori.in");
ofstream cout("culori.out");

#define MAXN 514

int cul[MAXN];
int v[MAXN/2];
int r = 0;

int main()
{
    int n;

    int ans = 0;
    cin >> n;

    for(int i = 0; i < 2 * n - 1; i ++)
    {
        cin >> cul[i];
        if(v[cul[i]] == 0)
        {
            v[cul[i]]++;
            r++;
        }
    }

    if(cul[0] != cul[2 * n - 2])
    {
        cout << ans;
        return 0;
    }
    else
        cout << r % 9901;

             return 0;
}