#include <iostream>
#include <cstring>
typedef long long ll;
using namespace std;
const int N = 2010;
ll dp[N];
bool st[N][N];

int main()
{
    int n;
    cin>>n;
    string s;
    cin>>s;

    //st[i][j]判断i~j是否为回文串
    for(int i = n - 1; i >= 0; i -- )
        for(int j = i; j < n; j ++ )
        {
            if(s[i] == s[j] && (j - i <= 1 || st[i + 1][j - 1]))
                st[i][j] = 1;
        }


    for(int i = 0; i < n; i ++ )
    {
        //显然0~i是=回文串的话不需要分割
        if(st[0][i])
            dp[i] = 0;
        else
        {
            //初始化为i 最坏情况就是前i+1个需要分割i下
            dp[i] = i;
            for(int j = 0; j < i; j ++ )
                if(st[j + 1][i])
                    dp[i] = min(dp[i], dp[j] + 1);
        }
    }

    cout<<dp[n - 1]<<endl;
}