cf 26A

#include<iostream>

using namespace std;

int main()
{
    int n, c = 0, ara[3001] = {0};
    cin >> n;

    for(int i = 2; i <= n; i++)
    {
        if(ara[i] == 0)
        {
            for(int j = i; j <= n; j += i) ara[j]++;
        }
        if(ara[i] == 2) c++;
    }
    cout << c << endl;
}