Ball Elimination

INF = (1<<30)

def f(i, j):
    if dp[i][j] is not None:
        return dp[i][j]

    if i==j+1:
        res = 0
    elif i==j:
        res = 1
    else:
        res = INF
        if a[i]==a[j]:
            res = f(i+1, j-1)
        else:
            for k in range(i, j):
                res = min(res, f(i, k)+f(k+1, j))
    dp[i][j] = res
    return dp[i][j]

n = int(input())
a = [int(w) for w in input().split()]

dp = [[None]*n for i in range(n)]

ans = f(0, n-1)
print(ans)