#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("popcnt,bmi2,fma,fma4,avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#include <bits/stdc++.h>
using namespace std;

int a[200001], b[200001];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n;
	cin >> n;
	for(int i = 0; i < 2 * n + 1; i++) cin >> a[i];
	while(n--) {
		for(int i = 0; i < n * 2 + 1; i++) {
			b[i] = a[i] + a[i + 1] + a[i + 2] == 3 ? a[i + 1] - a[i] == 1 or a[i + 1] - a[i] == -2 ? 1 : 2 : 0;
		}
		swap(a, b);
	}
	cout << a[0] << endl;
}