#include <iostream>

#include <cstdio>

#define REP(i,a,n) for(int i=a;i<=n;++i)

using namespace std;

const int N = 510, INF = 0x3f3f3f3f;

int n,a[N],dp[N][N];

int main() {

	scanf("%d",&n);

	REP(i,1,n) scanf("%d",a+i);

	REP(d,1,n) {

		for (int l=1,r=d;r<=n;++l,++r) {

			if (d==1) dp[l][r]=1;

			else if (d==2) dp[l][r]=a[l]==a[r]?1:2;

			else {

				dp[l][r]=INF;

				if (a[l]==a[r]) dp[l][r]=dp[l+1][r-1];

				REP(k,l,r-1) dp[l][r]=min(dp[l][r],dp[l][k]+dp[k+1][r]);

			}

		}

	}

	printf("%d\n", dp[1][n]);

}