---

#include <stdio.h>

#define NMAX 30

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

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

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

    return 0;
}

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

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

    for (int *p = a; result && p - a < *n; p++) {
        if (scanf("%d", p) != 1) {
            result = 0;
        }
    }

    return result;
}

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

    for (int *p = a; p - a < n; p++) {
        sum += *p;
    }

    return sum / n;
}

double variance(int *a, int n) {
    double result = 0.0;
    double avg = mean(a, n);

    for (int *p = a; p - a < n; p++) {
        double diff = *p - avg;
        result += diff * diff;
    }

    return result / n;
}

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

    for (int *p = a; p - a < n && result == 0; p++) {
        if (check_number(*p, mean_value, variance_value)) {
            result = *p;
        }
    }

    return result;
}

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

    if (number != 0 && number % 2 == 0 && number >= mean_value &&
        diff * diff <= 9.0 * variance_value) {
        result = 1;
    }

    return result;
}