#include <bits/stdc++.h>
using namespace std;
const int N = (int)1e5 + 7;
int n;
int v[N], f[N];
bool e[N];
int st, dr;
bool ok(int l, int r) {
  for (int i = 1; i <= n; i++) {
    e[i] = 0;
    f[i] = 0;
  }
  for (int i = l; i <= r; i++) {
    e[i] = 1;
    f[v[i]]++;
  }
  for (int i = 1; i < n + 1 - i; i++) {
    if (e[i] == 1 && e[n + 1 - i] == 0) {
      if (f[v[n + 1 - i]] > 0) {
        f[v[n + 1 - i]]--;
      } else {
        return 0;
      }
    }
    if (e[i] == 0 && e[n + 1 - i] == 1) {
      if (f[v[i]] > 0) {
        f[v[i]]--;
      } else {
        return 0;
      }
    }
    if (e[i] == 0 && e[n + 1 - i] == 0 && v[i] != v[n + 1 - i]) {
      return 0;
    }
  }
  int cntimp = 0;
  for (int i = 1; i <= n; i++) {
    if (f[i] % 2 == 1) {
      cntimp++;
    }
  }
  return (cntimp <= 1);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> v[i];
    f[v[i]]++;
  }
  int imp = 0;
  for (int i = 1; i <= n; i++) {
    if (f[i] % 2 == 1) {
      imp++;
    }
  }
  if (imp >= 2) {
    cout << "0\n";
    return 0;
  }
  bool pali = 1;
  for (int i = 1; i < n + 1 - i; i++) {
    if (v[i] != v[n + 1 - i]) {
      pali = 0;
    }
  }
  if (pali) {
    long long res = n * (long long)(n + 1) >> 1;
    cout << res << "\n";
    return 0;
  }
  st = 1;
  dr = n;
  while (v[st] == v[dr]) {
    st++;
    dr--;
  }
  int lo = st;
  int hi = dr;
  int prf = -1, suf = -1;
  while (lo <= hi) {
    int mid = (lo + hi) >> 1;
    if (ok(st, mid)) {
      prf = mid;
      hi = mid - 1;
    } else {
      lo = mid + 1;
    }
  }
  lo = 1;
  hi = n;
  while (lo <= hi) {
    int mid = (lo + hi) >> 1;
    if (ok(mid, dr)) {
      suf = mid;
      lo = mid + 1;
    } else {
      hi = mid - 1;
    }
  }
  int cntgood = 0;
  if (prf != -1) {
    cntgood += (dr - prf + 1);
  }
  if (suf != -1) {
    cntgood += (suf - st + 1);
  }
  long long res =
      cntgood * (long long)st - 1 + (st - 1LL) * (long long)(st - 1LL);
  cout << res << "\n";
  return 0;
}
