#include<bits/stdc++.h>
using namespace std;
//普通筛 
bool a(int n)
{
    for(int i = 2;i <= sqrt(n);++i)
        if(n%i == 0)
            return 0;	
    return 1;
}

int main(){
    int n,sum=1;
    cin >> n;
    for(int i=2;i<=n;++i)
    {
        if(i%2==0&&i!=1)
            continue;
        if(a(i))
			++sum;
    }
    cout << sum;
    return 0;
}