#include <iostream>
#include <fstream>
using namespace std;
ifstream f("pairs.in");
ofstream g("pairs.out");
int n, i, j, k = 0, aux1, aux2, cate = 0, doiuri;
bool x[1000001];

int main()
{
    f >> n;
    int v[n+1];

    /// Eratostene pana la 1.000.000
    for(i = 2; i*i <= 1000000; i++)
        if(x[i] == 0)
        for(j = 2; i*j <= 1000000; j++)
            x[i*j] = 1;

    for(i = 1; i <= n; i++) {
        f >> v[i];
    }

    for(i = 1; i <= n; i++) {
        if(x[v[i]] == 0) {
            if(v[i] == 2) {
                for(j = 1; j <= n; j++) {
                    if(v[j] != 2)
                        if(v[j]%2 == 1)
                            k++;
                }
                doiuri++;
            }
            else {
                cate++;
            }
        }
    }
    if(doiuri > 1)
        k = k + cate*(n-1-doiuri-1);
    else if(doiuri == 1)
        k = k + cate*(n-1-1);
    else k = k + cate*(n-1);



    g << k;
    return 0;
}