#include <iostream>
#include <iomanip>

using namespace std;


int main(int argc, const char * argv[]) {
    // insert code here...
    
    int maxNumber;
    int countPrime=0;
    bool judgePrime = true;
    
    while(cin >> maxNumber){
        for(int i=2; i<=maxNumber;i++){
            for(int j=2; j<i;j++){
                if(i%j==0){
                    judgePrime = false;
                }
            }
            if(judgePrime){countPrime++;}
            judgePrime = true;
        }
        cout << countPrime << endl;
    }
    

    return 0;
}

