#include<bits/stdc++.h>
using namespace std;
int n, a, b, sum,c;
bool z;
int hwss(int a) {//判断素数
	for (int i = 2; i * i <= a; i++) {
		if (a % i == 0)	{
			return false;
		}
	}
	return true;
}
int main() {
	cin >> n;
	for (int i = 11; i <= n; i++) {
		a = i;
		z = hwss(a);
		if (z == 1) { 
		c=i;
			while (c) {
				int yu = c % 10;
				sum = sum * 10 + yu;//这里怎么整
				c/= 10;

			}


			if (sum == i) {

				b++;
			}

		}
	}
	cout << b;
	return 0;
}