#include<stdio.h>
#include<math.h>
#define DB(x) 
int prime[80000];
int GetPrime(int num);

int main(){
	int count = GetPrime(1000000);
	DB(printf("%d\n",count));
	int n,ans[100],cor = 0;
	int i;
	while(scanf("%d",&n) != EOF){
		for(i = 0;n >= prime[i] && i < count;i++);
		ans[cor] = i;
		cor++;
	}
	for(i = 0;i < cor;i++)
		printf("%d\n",ans[i]);
	return 0;
}

int GetPrime(int num){
	int i,j,count = 0;
	int sqnum = sqrt((double)num);
	for(i = 2;i <= num;i++){
		for(j = 0;j < count;j++){
			if(prime[j] > sqnum)
				goto COUNT;
			if(i%prime[j] == 0)
				break;
		}
		if(j < count)
			continue;
		COUNT:
		prime[count] = i;
		count++;
	}
	return count;
}