#include <iostream>
using namespace std;

int main()
{
    int n;
    cin >> n;
    n = n * 2 + 1;
    int a[200005];
    for(int i = 0; i < n; i++) cin >> a[i];
    for(int i = 0; i < n - 4; i++){
        if(a[i] != a[i + 4]){
            cout << 0 << endl;
            return 0;
        }
    }
    for(int i = 1; i < n - 2; i += 2){
        if(a[i] != a[i + 2]){
            cout << 0 << endl;
            return 0;
        }
    }
    if(n % 4 == 1){
        if((a[0] + 1) % 3 == a[1] && (a[1] + 1) % 3 == a[2]) cout << 2 << endl;
        else if((a[0] + 2) % 3 == a[1] && (a[1] + 2) % 3 == a[2]) cout << 1 << endl;
        else cout << 0 << endl;
    }
    else{
        if((a[0] + 1) % 3 == a[1] && (a[1] + 1) % 3 == a[2]) cout << 1 << endl;
        else if((a[0] + 2) % 3 == a[1] && (a[1] + 2) % 3 == a[2]) cout << 2 << endl;
        else cout << 0 << endl;
    }
}