#include<cstdio>
#include<math.h>

/*
unsigned long N;
unsigned long T;

int s[2000100];
*/
int main(){
	/*unsigned long i,j;
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);*/
	
	scanf("%ld",&N);
	/*for(i=2;i<=N;i++){
		if(s[i]==0){
			++T;
			for(j=2;j<=N/i;j++){
				s[i*j]=1;
			}
		}
	}
	*/
	/*printf("%ld",T);*/
	
	return 0;
}