#include<stdio.h>
int main()
{	
	
	int x;
	while(1==1){
		scanf("%d",&x);
		if(x!=0){
			int i,s=0;	
				for(i=2;i<=x;i++){
					int c=0;
					int n;
					for(n=2;n<=i/2;n++){
						if(i%n==0){
							c++;
							break;
						}
						
					}
					if(c==0){
							s++;
						}	
				}
				printf("%d ",s);
		}else{
			break;
		}
	
		
	}
	
	
	return 0;
	
}
/**************************************************************
	Problem: 1176
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/