#include <iostream>
#include <complex>
int main(){
	while(1){
		int ans=0;
		int n;
		if(scanf("%d",&n)==EOF)break;
		if(n==1){
			std::cout<<0<<std::endl;
		}else{
			if(n>=2)ans++;
			if(n>=3)ans++;
			if(n>=5)ans++;
			if(n>=7)ans++;
			if(n>=11){
				for(int i=11;i<=n;i+=2){
					bool prime=true;
					int iSqrt=sqrt(i);
					for(int k=3;k<=iSqrt;k+=2){
						if(i%k==0){
							prime=false;
							break;
						}
					}
					if(prime)ans++;
				}
			}
		std::cout<<ans<<std::endl;
		}
	}
}
