---

/*
    Search module for the desired value from data array.

    Returned value must be:
        - "even"
        - ">= mean"
        - "<= mean + 3 * sqrt(variance)"
        - "!= 0"

        OR

        0
*/

#include <math.h>
#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 main() {
    int n, data[NMAX];

    if (!input(data, &n)) {
        printf("n/a");
        return 0;
    }

    printf("%d", search(data, n));

    return 0;
}

int input(int* a, int* n) {
    if (scanf("%d", n) != 1) return 0;
    if (*n <= 0 || *n > NMAX) return 0;

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

    return 1;
}

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

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

    return sum / n;
}

double variance(int* a, int n) {
    double m = mean(a, n);
    double sum = 0;

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

    return sum / n;
}

int search(int* a, int n) {
    double m = mean(a, n);
    double upper = m + 3 * sqrt(variance(a, n));

    for (int* p = a; p - a < n; p++) {
        if (*p != 0 && *p % 2 == 0 && *p >= m && *p <= upper) return *p;
    }

    return 0;
}