#include<fstream>
#define DIM 270
#define mod 9901
using namespace std;
int n, i, j, k, L;
int a[2 * DIM][2 * DIM], v[2 * DIM];
ifstream fin("culori.in");
ofstream fout("culori.out");
int main(){
    fin>> n;
    n = 2 * n - 1;
    for(i = 1; i <= n; i++){
        fin>> v[i];
        a[i][i] = 1;
    }
    for(L = 1; L <= n; L++){
        for(i = 1; i <= n - L + 1; i++){
            j = i + L - 1;
            if(v[i] == v[j]){
                for(k = i + 1; k < j; k++){
                    if(v[i + 1] == v[k]){
                        a[i][j] += a[i + 1][k] * a[k][j - 1];
                    }
                }
            }
        }
    }
    fout<< a[1][n] <<"\n";
    return 0;
}