#include <fstream>

using namespace std;
ifstream cin("grigo.in");
ofstream cout("grigo.out");
bool v[100001];
int main()
{
    int i,x,n,sum = 1;
    cin >> n;
    for(i=1;i<=n;i++){
        cin >> x;
        v[x-1] = true;
    }
    for(i=1;i<=n;i++){
        if(!v[i])
            sum = sum*i % 1000003;
    }
    cout << sum;
    return 0;
}