#include <iostream>

#include <algorithm>

#include <cstdio>

#include <math.h>

#include <set>

#include <map>

#include <queue>

#include <string>

#include <string.h>

#include <bitset>

#define REP(i,a,n) for(int i=a;i<=n;++i)

#define PER(i,a,n) for(int i=n;i>=a;--i)

#define hr putchar(10)

#define pb push_back

#define lc (o<<1)

#define rc (lc|1)

#define mid ((l+r)>>1)

#define ls lc,l,mid

#define rs rc,mid+1,r

#define x first

#define y second

#define io std::ios::sync_with_stdio(false)

#define endl '\n'

#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;})

using namespace std;

typedef long long ll;

typedef pair<int,int> pii;

const int P = 1e9+7, INF = 0x3f3f3f3f;

ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}

ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}

ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}

inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}

//head

#ifdef ONLINE_JUDGE

const int N = 1e6+10;

#else

const int N = 111;

#endif

int n, m, k, t;

int f[N], a[N], c[N];

int main() {

	a[0] = -1;

	scanf("%d", &n);

	REP(i,1,n) scanf("%d",a+i),++f[a[i]];

	REP(i,1,n) m += f[i]&1;

	if (m>1) return puts("0"),0;

	int pos = 1, len = 0;

	while (a[pos]==a[n-pos+1]) f[a[pos++]]-=2;

	if (pos>n) return printf("%lld\n",(ll)n*(n+1)/2),0;

	PER(i,1,n-pos+1) {

		if (2*++c[a[i]]>f[a[i]]) {

			if (i>n-i+1||a[i]!=a[n-i+1]) break;

			if (i==n-i+1&&f[a[i]]%2==0) break;

		}

		++len;

	}

	memset(c,0,sizeof c);

	REP(i,pos,n) {

		if (2*++c[a[i]]>f[a[i]]) {

			if (i<n-i+1||a[i]!=a[n-i+1]) break;

			if (i==n-i+1&&f[a[i]]%2==0) break;

		}

		++len;

	}

	printf("%lld\n", (ll)pos*(pos+len));

}