#include <iostream>
#include <cstdio>

using namespace std;
int n;
int pr[170]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009};
bool prime(int x)
{
	int i;
	for(i=0;pr[i]*pr[i]<=x;i++)
	{
		if(x%pr[i]==0) 
		{
		 return false;
		}
	}
	return true; 
}

int main()
{
    while(cin>>n) {
        if(n==1) {
            printf("0\n");
            continue;
        }
        int ans=1;
        if(n==2) {
            printf("%d\n", ans);
            continue;
        }
        for(int i=3; i<=n; i+=2)
           if(prime(i)) ans++;
        printf("%d\n", ans);
    }
    return 0;
}
