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

typedef long long ll;
typedef double lf;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;

#define TRACE(x) cerr << #x << ' ' << x << endl
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define _ << ' ' <<

#define fi first
#define sec second
#define se second
#define mp make_pair
#define pb push_back

const int MAXN = 400100;
const int B[] = {1337, 10007};
const int MOD[] = {int(1e9) + 7, int(1e9) + 9};

int n;
string s;

int pot[2][MAXN];

int add(int a, int b, int M) {
  a += b;
  if (a >= M) a -= M;
  if (a < 0)  a += M;
  return a;
}

int mul(int a, int b, int M) {
  return (ll)a * b % M;
}

pii H[MAXN], rev[MAXN];


pii get(int a, int b) {
  pii k = {0, 0};
  if (a) k = {mul(H[a - 1].fi, pot[0][b], MOD[0]), mul(H[a-1].sec, pot[1][b], MOD[1])};
  return {add(H[a + b - 1].fi, -k.fi, MOD[0]), add(H[a + b - 1].sec, -k.sec, MOD[1])};
}

pii get_rev(int a, int b) {
  pii k = {0, 0};
  if (a < n - 1) k = {mul(rev[a + 1].fi, pot[0][b], MOD[0]), mul(rev[a+1].sec,pot[1][b], MOD[1])};
  return {add(rev[a - b + 1].fi, -k.fi, MOD[0]), add(rev[a - b + 1].sec, -k.sec, MOD[1])};
}



int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);

  cin >> n >> s;
  
  REP(j, 2) {
    pot[j][0] = 1;
    FOR(i, 1, MAXN) pot[j][i] = mul(pot[j][i-1], B[j], MOD[j]);
  }
  
  H[0] = {s[0], s[0]};

  FOR(i, 1, n) {
    H[i] = {add(mul(H[i-1].fi, B[0],MOD[0]), s[i], MOD[0]), add(mul(H[i-1].sec,B[1], MOD[1]), s[i], MOD[1])};
  }

  rev[n - 1] = {s[n - 1], s[n - 1]};
  for (int i = n - 2; i >= 0; i--) {
    rev[i] = {add(mul(rev[i+1].fi, B[0],MOD[0]), s[i],MOD[0]), add(mul(rev[i+1].sec,B[1],MOD[1]), s[i],MOD[1])};
  }

  if (H[n - 1] == rev[0]) {
    cout << 0 << endl;
    return 0;
  }

  FOR(i, 1, n) {
    if (get(i, n - i) == get_rev(n - 1, n - i)) {
      cout << i << endl;
      return 0;
    }
  }

  return 0;
}