#!/usr/bin/python3
import sys

sys.setrecursionlimit(650000)

INF = int(1e9)

n = int(sys.stdin.readline())
val = [0] + [int(sys.stdin.readline()) for _ in range(n)]

dp = [[-1] * (n + 1) for _ in range(n + 1)]

def solve(l, r):
  if l == r: return 0
  if dp[l][r] != -1: return dp[l][r]
  ans = INF
  for i in range(l, r):
    sol = solve(l, i) + solve(i + 1, r) + (1 if val[l] != val[i + 1] else 0)
    ans = min(ans, sol)
  dp[l][r] = ans
  return ans

print (solve(0, n))