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

#define LL long long
#define LD long double
#define PII pair<int, int>
#define VI vector<int>
#define VPII vector<PII>
#define f first
#define s second
#define MP make_pair
#define PB push_back
#define endl '\n'
#define SIZ(c) (int)(c).size()
#define ALL(c) (c).begin(), (c).end()
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, b, e) for (int i = (b); i <= (int)(b); i++)
#define FORD(i, b, e) for (int i = (b); i >= (int)(b); i--)
#define ll LL
#define st f
#define nd s
#define mp MP
#define pb PB
#define eb emplace_back
#define siz(c) SIZ(c)
const int inf = 1e9 + 7;
const LL INF = 1e18L + 7;

#define sim template<class n
sim, class s> ostream & operator << (ostream &p, pair<n, s> x)
{return p << "<" << x.f << ", " << x.s << ">";}
sim> auto operator << (ostream &p, n y) ->
typename enable_if<!is_same<n, string>::value, decltype(y.begin(), p)>::type
{int o = 0; p << "{"; for (auto c : y) {if (o++) p << ", "; p << c;} return p << "}";}
void dor() {cerr << "\n";}
sim, class...s> void dor(n p, s...y) {cerr << p << " "; dor(y...);}
sim, class s> void mini(n &p, s y) {if (p > y) p = y;}
sim, class s> void maxi(n &p, s y) {if (p < y) p = y;}

#ifdef DEB
#define debug(...) dor(__FUNCTION__, ":", __LINE__, ": ", __VA_ARGS__)
#else
#define debug(...)
#endif

#define I(x) #x " =", (x), " "

const int N = 4e5+7;

int n;

string s;

int p[2][N];

bool is_palindrome(int l, int r)
{
	return p[(l + r + 1) % 2][(l + r + 1) / 2] >= (r - l + 1) / 2;
}

int32_t main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> s;
	
	for(int z = 0, l = 0, r = 0; z < 2; z++, l = 0, r = 0)
	{
		for(int i = 0; i < n; i++)
		{
			if(i < r) p[z][i] = min(r - i + !z, p[z][l + r - i + !z]);
			int L = i - p[z][i], R = i + p[z][i] - !z;
			while(L - 1 >= 0 && R + 1 < n && s[L - 1] == s[R + 1]) p[z][i]++, L--, R++;
			if(R > r) l = L, r = R;
		}	
	}
	
	for(int i = n; i >= 1; --i)
	{
		if(is_palindrome(n-i, n-1))
		{
			cout << n - i << endl;
			return 0;
		}
	}
}