// created:  2025-03-11 10:22:49
#include<cstdio>
#include<cctype>
#include<algorithm>
#define F(i,l,r) for(int i=(l),i##_end=(r);i<i##_end;++i)
#define I128 //||is_same<T,__int128_t>::value||is_same<T,__uint128_t>::value
using namespace std;
template<typename T>constexpr bool is_integral_128=(bool)is_integral<T>::value I128;
template<typename T>struct read_dec1{enable_if_t<is_integral_128<T>,T> &x;};
constexpr struct read_dec1_conv{template<typename T>read_dec1<T> operator+(T &x)const{return read_dec1<T>{x};}}D;
template<typename T>enable_if_t<is_integral_128<T>,void> readmain(T &x)
{
	bool neg=false;int c=getchar();
	for(;!isdigit(c);c=getchar())if(c=='-')neg=true;
	for(x=0;isdigit(c);c=getchar())x=(T)(10*x+(c-'0'));
	if(neg)x=-x;
}
template<typename T>void readmain(read_dec1<T> &y){readmain(y.x);--y.x;}
template<typename T>T& read(T &&x){readmain(x);return x;}
template<typename T,typename ...Tr>void read(T &&x,Tr&&... r){readmain(x);read(r...);}
typedef unsigned long long ull;
constexpr int N=505,MOD=998244353;
void reduce(int &x){if(x>=MOD)x-=MOD;}
void reduce_(int &x){if(x<0)x+=MOD;}
int n,a[N],f[N][N][2];
int main()
{
	read(n);
	F(i,0,n)--read(a[i]);
	F(i,0,n+1)f[i][i][0]=1;
	for(int l=n;~--l;)F(r,l+1,n+1)
	{
		if(a[l]==a[r-1])
		{
			f[l][r][0]=1;
			f[l][r][1]=r-l==1;
			continue;
		}
		F(i,l+1,r)f[l][r][1]=(int)((f[l][r][1]+(ull)f[l][i][1]*f[i][r][0])%MOD);
		if(a[l]==a[l+1])reduce_(f[l][r][0]-=f[l+2][r][0]);
		if(a[r-1]==a[r-2])reduce_(f[l][r][0]-=f[l][r-2][0]);
		reduce(f[l][r][0]+=f[l][r][1]);
		reduce(f[l][r][0]+=f[l][r][1]);
		reduce_(f[l][r][1]=f[l][r][0]-f[l][r][1]);
	}
	printf("%d\n",f[0][n][0]);
	return 0;
}