#include <bits/stdc++.h>
using namespace std;
int main(){
    int N;
    cin >> N;
    vector<int> A(2 * N + 1);
    for(int i = 0; i < 2 * N + 1; i++) cin >> A[i];
    for(int i = 0; i < 3; i++){
        vector<int> s(2 * N + 1), t(2 * N + 1);
        for(int j = 1; j < 2 * N + 1; j += 2){
            s[j] = i;
            t[j] = i;
        }
        int l = (i + 2) % 3;
        int r = (i + 1) % 3;
        for(int j = 0; j < 2 * N + 1; j += 2){
            s[j] = l;
            t[j] = r;
            l = 3 - l - i;
            r = 3 - r - i;
        }
        if(A == s){
            if(N % 2){
                cout << 1 << endl;
            }
            else{
                cout << 2 << endl;
            }
            return 0;
        }
        else if(A == t){
            if(N % 2){
                cout << 2 << endl;
            }
            else{
                cout << 1 << endl;
            }
            return 0;
        }
    }
    cout << 0 << endl;
}