#include <bits/stdc++.h>
using namespace std;
int read() {
  char ch = getchar();
  int x, f = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  x = ch - '0';
  while (1) {
    ch = getchar();
    if (ch < '0' || ch > '9') break;
    x = x * 10 + ch - '0';
  }
  return x * f;
}
const int maxn = 510;
const int inf = 0x7fffffff;
int n, a[maxn], dp[maxn][maxn];
int main() {
  n = read();
  for (int i = 0; i < n; i++) a[i] = read();
  for (int i = 1; i <= n; i++) {
    for (int j = 0, k = i - 1; k < n; j++, k++) {
      if (i == 1) {
        dp[j][k] = 1;
        continue;
      }
      dp[j][k] = dp[j + 1][k] + 1;
      for (int p = j + 2; p <= k; p++)
        if (a[p] == a[j])
          dp[j][k] = min(dp[j][k], dp[j + 1][p - 1] + dp[p + 1][k]);
      if (a[j] == a[j + 1]) dp[j][k] = min(dp[j][k], dp[j + 2][k] + 1);
    }
  }
  printf("%d\n", dp[0][n - 1]);
  return 0;
}
