#include<stdio.h>
#include<iostream>
#include<cmath>
#include<string>
#include<algorithm>
using namespace std;
int isprim(int t) {//判断素数
	int sum = 0;
	for (int i = 1; i * i <= t; i++) {
		if (t % i == 0)sum++;
	}
	if (sum == 1)
		return 1;
}
int hui(int t) {//判断回文数
	int a, b, c, sum = 0;

	if(t<100){//两位数
		a = t % 10;
		b = t / 10;
		sum = a * 10 + b;
	}
	else {//三位数
		a = t % 10;
		t /= 10;
		b = t % 10;
		c = t / 10;
		sum = a * 100 + b * 10 + c;
	}
	if(t==sum)
		return 1;

}
int main(){
	int n;
	int s= 0;
	cin >> n;
	for (int i = 11; i <= n; i++)
		if ((isprim(i) == 1 )&& (hui(i) == 1))
			s++;
	cout << s;
	return 0;
}