#include<cstdio>

const long MAX=2000100;

long i,j,n,nr;
unsigned char v[(MAX >> 3)+2];

int main(){
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%ld",&n);
	for(i=1;((i*i) << 1)+(i << 1)<=n;i++)
		if((v[i >> 3] & (1 << (i & 7)))==0)
			for(j=((i*i) << 1)+(i << 1);(j << 1)+1<=n;j+=(i << 1)+1)
				v[j >> 3]|=(1 << (j & 7));
	nr=1;
	for(i=1;i<=n;i++)
		if((v[i >> 3] & (1 << (i & 7)))==0)
			if((i << 1)+1<=n){
				nr++;
			}
	printf("%ld\n",nr);
	fclose(stdin);
	fclose(stdout);
	return 0;
}