#include<iostream>
#include<cmath>
using namespace std;

bool panduan(int i) {
    
    for (int j = 2; j < i / 2; j++) {

        if (i % j == 0) {

            return false;

        }

    }
    return true;
}


int sum1= 0;
void huanwei(int i) {

    int a, b, c ,sum2;
    a = i / 100;
    b = (i % 100) / 10;
    c = i % 10;
    sum2 =  c * 100 + b * 10 + a;
    if (i != sum2 && panduan(sum2)) {

        cout <<"幻影素数对："<< i <<" "<<sum2<<endl;
        sum1++;
    }
    //cout << endl;
}


int main() {
    
    int a = 100, b = 999,sum=0;
    for (int i = a; i <= b; i++) {
        sum = 0;
        for (int j = 1; j <= i; j++) {

            if (i % j == 0) {

                sum++;

            }

        }
        if (sum == 2) {

            //cout << i << " ";
            huanwei(i);
            
        }
        
    }
    cout << sum1 << endl;
}