#include <iostream>

using namespace std;

int n, i;

struct node{
    char key;
    node *next;
};

node *p, *u, *r;

bool palindrom(node *l){
    node *u = l;
    char v[10003], nr = 0;
    while(u!=NULL){
        v[++nr] = u->key;
        u = u->next;
    }
    for(int i = 1;i<=nr/2;i++)
        if(v[i] != v[nr-i+1])
            return false;
    return true;

}

int main(){
    p = new node;
    cin>>n>>p->key;
    u = p;
    for(i=1;i<=n;i++){
        u->next = new node;
        cin>>u->next->key;
        u = u->next;
    }
    u->next = NULL;
    if(palindrom(p))
        cout<<"ESTE PALINDROM";
    else
        cout<<"NU ESTE PALINDROM";
    return 0;
}