#include<bits/stdc++.h>
using namespace std ;

#define M 1000000007
#define MM 998244353
#define ll long long
#define pb push_back
#define mem0(a) memset(a,0,sizeof(a))
#define mem1(a) memset(a,-1,sizeof(a))
#define memf(a) memset(a,false,sizeof(a))
#define all(v) v.begin(),v.end()
#define sz(a) (ll)a.size()
#define F first
#define S second
#define PI 3.1415926536
#define INF 2e18
#define endl "\n"
#define llevel 20
ll power(ll b,ll e,ll m)
{
	if(e==0) return 1;
	if(e&1) return b*power(b*b%m,e/2,m)%m;
	return power(b*b%m,e/2,m);
}
ll power( ll b, ll e)
{
	if(e==0) return 1;
	if(e&1) return b*power(b*b,e/2);
	return power(b*b,e/2);
}
ll n;
string str;
const int N=800;
ll dp[N][N],ans[N][N];
vector<int> zFunction(string &s)
{
	int n=sz(s),l,r,i;
	vector<int> z(n);
	z[0]=n;
	l=r=0;
	for(i=1;i<n;++i)
	{
		if(i<=r)
			z[i]=min(r-i+1,z[i-l]);
		while(i+z[i]<n && s[z[i]]==s[z[i]+i])
			++z[i];
		if(i+z[i]-1>r)
		{
			l=i;r=i+z[i]-1;
		}
	}
	return z;
}
ll calc(string s)
{
	vector<int> vv=zFunction(s);
	ll kk=sz(s);
	ll ans=kk;
	for(ll i=1;i<kk;++i)
	{
		if(kk%i==0 && i+vv[i]==kk)
			ans=min(ans,i);
	}
	return ans;
}

ll getans(ll i,ll j)
{
	if(i==j)
		return 1;
	if(ans[i][j]!=-1)
		return ans[i][j];
	if(dp[i][j]<j-i+1)
	{
		return ans[i][j]=getans(i,i+dp[i][j]-1);
	}
	ll ret=j-i+1;
	for(ll kk=i;kk<j;++kk)
	{
		ret=min(getans(i,kk)+getans(kk+1,j),ret);
	}
	return ans[i][j]=ret;
}
int _runtimeTerror_()
{
	ll i,j;
	cin>>n>>str;
	mem1(ans);
	for(i=0;i<n;++i)
	{
		for(j=i;j<n;++j)
		{
			if(j==i)
			{
				dp[i][j]=1;continue;
			}
			string t=str.substr(i,j-i+1);
			dp[i][j]=calc(t);
		}
	}
	cout<<getans(0,n-1);
	return 0;
}

int main()
{
	ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	#ifdef runSieve
		sieve();
	#endif
	#ifdef NCR
		initialize();
	#endif
	int TESTS=1;
	//cin>>TESTS;
	while(TESTS--)
		_runtimeTerror_();
	return 0;
}