#include <bits/stdc++.h>
using namespace std;
inline int add(int a, int b, int m = 1000000007) {
  a += b;
  if (a >= m) a -= m;
  return a;
}
inline int mul(int a, int b, int m = 1000000007) {
  return (int)(((long long)a * (long long)b) % m);
}
inline int norm(int x, int m = 1000000007) {
  if (x >= m) x %= m;
  if (x < 0) x += m;
  return x;
}
inline int neg(int x, int m = 1000000007) {
  x = -x;
  return norm(x);
}
int c[501];
int dp[501][501];
int f(int i, int j) {
  if (i == j) return 1;
  if (i == j - 1) return 2 - (int)(c[i] == c[j]);
  int &ans = dp[i][j];
  if (ans != -1) return ans;
  ans = 1000000007;
  for (int k = i; k <= j - 1; ++k) {
    ans = min(ans, f(i, k) + f(k + 1, j));
  }
  if (c[i] == c[j]) ans = min(ans, f(i + 1, j - 1));
  return ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> c[i];
  memset(dp, -1, sizeof(dp));
  cout << f(1, n);
  return 0;
}
