#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
#include<cstdlib>
using namespace std;
#define LL long long
#define MODER 1000000007
LL n,a[105],dp[105][105],c[105][105];
void fun()
{
    c[0][0]=1;
    c[1][0]=1;
    for(int i=1;i<=100;i++)
    {
        c[i][i]=1;
        c[i][0]=1;
        for(int j=1;j<i;j++)
        {
            c[i][j]=(c[i-1][j]+c[i-1][j-1])%MODER;
        }
    }
}
LL dfs(int l,int r)
{
    if(dp[l][r]!=-1)
        return dp[l][r];
    if(l==r) return dp[l][r]=1;
    dp[l][r]=(dfs(l+1,r)+dfs(l,r-1))%MODER;
    for(int k=l+1;k<r;k++)
    {
        if(a[k-1]!=a[k+1])
            continue;
        dp[l][r]=(dp[l][r]+dfs(l,k-1)%MODER*dfs(k+1,r)%MODER*c[r-l][k-l]%MODER)%MODER;
    }
    return dp[l][r]%MODER;
}
int main()
{
    fun();
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i]);
        memset(dp,-1,sizeof(dp));
        printf("%I64d\n",dfs(1,n)%MODER);
    }
    return 0;
}