#include <algorithm>
#include <iostream>
#include <iomanip>
#include <complex>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <cstdio>
#include <cmath>
#include <map>
#include <set>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,102400000")

long long mod = 1000000007LL;

long long power(long long a, long long b)
{
    long long ret = 1;
    while(b)
    {
        if(b&1)
            ret = (ret * a) % mod;
        a = (a * a) % mod;
        b /= 2;
    }
    return ret;
}


long long inv(long long x)
{
    return power(x, mod - 2);
}

long long dp[102][102];
int x[101];
long long C[101][101];

int MAIN()
{
    for(int i = 0; i <= 100; i++)
    {
        C[i][0] = C[i][i] = 1;
        for(int j = 1; j < i; j++)
            C[i][j] = (C[i-1][j-1] + C[i-1][j]) % mod;
    }

    int n;
    while(cin >> n)
    {
        for(int i = 1; i <= n; i++)
            cin >> x[i];
        for(int i = 0; i <= n+1; i++)
            for(int j = 0; j <= n+1; j++)
                dp[i][j] = 1;

        for(int s = 1; s <= n; s++)
            for(int L = 1; L+s-1 <= n; L++)
            {
                int R = s + L;
                dp[L][R] = 0;
                for(int j = L; j <= R; j++)
                {
                    if(j != L && j != R && x[j-1] != x[j+1])
                        continue;
                    long long t = 1;
                    t *= C[R-L][j-L];
                    t *= dp[L][j-1];
                    t %= mod;
                    t *= dp[j+1][R];
                    dp[L][R] += t;
                    dp[L][R] %= mod;
                }
            }

        cout << dp[1][n] << endl;
    }
    
    return 0;
}

int main()
{
    #ifdef LOCAL_TEST
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    #endif
    ios :: sync_with_stdio(false);
    cout << fixed << setprecision(16);
    return MAIN();
}