#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int issimple(int n){
    int sqrtn = (int)sqrt(n)+1;
    int i;
    
    if(sqrtn-1 < 2){
        return 1;
    }
    
    for(i=2; i<= sqrtn; i++){
        if(n % i == 0){
            return 0;
        }
    }
    
    return 1;
}

int main()
{
    int arr[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 4, 7, 5};
    int length = sizeof(arr)/sizeof(arr[0]);
    int s = 0;
    int count = 0;
    int i;
    
    for(i = 0; i < length; i++ ){
        if( issimple(arr[i]) == 0 && i % 2 == 0){
            count++;
            s += arr[i];
        }
    }
    if (count == 0){
        printf("0");
    }
    else{
        printf("%d", s/count);
    }
    return 0;
}