#include <fstream>
#include <iostream>

using namespace std;

const int MAX_N = 257;

int n;
int v[MAX_N];

int ans;

int TT[MAX_N];

int DFS(int at, int lvl) {
    if(at == n) {
        return (lvl == 1);
    }


    TT[lvl + 1] = v[at];
    int ret = DFS(at + 1, lvl + 1);

    if(v[at + 1] == TT[lvl]) {
        ret += DFS(at + 1, lvl - 1);
    }
    return ret;

}

int main() {
    ifstream in("culori.in");
    in >> n;

    n = 2 * n - 1;

    for(int i = 1 ; i <= n ; ++i)
        in >> v[i];

    ofstream out("culori.out");
    out << DFS(1, 1) << "\n";
}