---

#include <stdio.h>

#define NMAX 30

int check_tail(void);
int input(int *a, int *n);
double mean(int *a, int n);
double variance(int *a, int n);
int is_good_number(int number, double mean_value, double variance_value);
int search(int *a, int n);

int main(void) {
    int n;
    int data[NMAX];

    if (input(data, &n)) {
        printf("%d", search(data, n));
    } else {
        printf("n/a");
    }

    return 0;
}

int check_tail(void) {
    int ch;
    int result = 1;

    while ((ch = getchar()) != '\n' && ch != EOF) {
        if (ch != ' ' && ch != '\t') {
            result = 0;
        }
    }

    return result;
}

int input(int *a, int *n) {
    int result = 1;
    int i = 0;

    if (scanf("%d", n) != 1 || *n <= 0 || *n > NMAX) {
        result = 0;
    }

    while (result && i < *n) {
        if (scanf("%d", a + i) != 1) {
            result = 0;
        }

        i++;
    }

    if (result && !check_tail()) {
        result = 0;
    }

    return result;
}

double mean(int *a, int n) {
    double sum = 0.0;
    int i = 0;

    while (i < n) {
        sum += *(a + i);
        i++;
    }

    return sum / n;
}

double variance(int *a, int n) {
    double mean_value = mean(a, n);
    double sum = 0.0;
    double diff;
    int i = 0;

    while (i < n) {
        diff = *(a + i) - mean_value;
        sum += diff * diff;
        i++;
    }

    return sum / n;
}

int is_good_number(int number, double mean_value, double variance_value) {
    int result = 0;
    double diff;

    if (number != 0 && number % 2 == 0 && number >= mean_value) {
        diff = number - mean_value;

        if (diff * diff <= 9.0 * variance_value) {
            result = 1;
        }
    }

    return result;
}

int search(int *a, int n) {
    int result = 0;
    int i = 0;
    double mean_value = mean(a, n);
    double variance_value = variance(a, n);

    while (result == 0 && i < n) {
        if (is_good_number(*(a + i), mean_value, variance_value)) {
            result = *(a + i);
        }

        i++;
    }

    return result;
}