#include <iostream>
#include <vector>

using namespace std;

const int M = 1000067;
bool pie[M];

void sito() {
    for (int i = 2; i < M-1; i++) {
        pie[i] = true;
    }
    pie[0] = pie[1] = false;
    for (int p = 2; p * p < M; p++) {
        if (pie[p]!=0) {
            for (int i = p * p; i < M; i += p) {
                pie[i] = false;
            }
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    sito();
    
    long int n;
    cin>>n;
    
    long long l2 = 0;
    long long war = 0;
    
    for (int i = 0; i < n; i++) {
        int a;
        cin >> a;
        if (a == 2) 
            l2++;
         else if (pie[a + 2]==1) 
            war++;
        
    }
    
    cout << l2 * war << "\n";
    
    return 0;
}