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

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

#define pb push_back
#define x first
#define y second

typedef long long ll;
typedef long double lf;

const int BASE1 = 31337;
const int BASE2 = 10007;
const int MOD1 = 1000000007;
const int MOD2 = 1000000009;

const int MAXN = 500500;

inline int add(int a, int b, int mod) { return a + b >= mod ? a + b - mod : a + b; }
inline int sub(int a, int b, int mod) { return a - b < 0 ? a - b + mod : a - b; }
inline int mul(int a, int b, int mod) { return (ll)a * b % mod; }


int n;
char s[MAXN];

int main(void) {
  scanf("%d", &n);
  scanf("%s", s);

  int h1l = 0;
  int h2l = 0;
  int h1r = 0;
  int h2r = 0;

  int p1 = 1;
  int p2 = 1;

  int ans = n - 1;
  for (int i = n - 1; i >= 0; --i) {
    h1l = add(h1l, mul(p1, s[i], MOD1), MOD1);
    h2l = add(h2l, mul(p2, s[i], MOD2), MOD2);
    h1r = add(s[i], mul(h1r, BASE1, MOD1), MOD1);
    h2r = add(s[i], mul(h2r, BASE2, MOD2), MOD2);
    p1 = mul(p1, BASE1, MOD1);
    p2 = mul(p2, BASE2, MOD2);
    if (h1l == h1r && h2l == h2r) {
      ans = min(ans, i);
    }
  }

  printf("%d\n", ans);

  return 0;
}