#include <iostream>
#include <cmath>
using namespace std;
bool isPrime(int n) {
if (n == 0) return 0;
if (n == 1) return 0;
for (int i = 2; i <= sqrt(n); i++) {
if (n % i == 0)
return 0;
}
return 1;
}
int main() {
int arr[] = {4, 8, 17, 5, 9, 22, 21, 13, 18, 99};
int len = sizeof(arr) / sizeof(int), max = arr[0];
for (int i = 0; i < len; i++) {
if (isPrime(arr[i])) { // 17 5 13
if (max < arr[i]) {
max = arr[i];
}
}
}
cout << max;
}
/*
run:
17
*/