#include<stdio.h>
FILE *f1,*f2;
long a,b,i,j,n,v[400000];
int main(){
	f1=fopen("ciur.in","r");
	f2=fopen("ciur.out","w");
	fscanf(f1,"%ld",&n);
	a=3;
	j=2;
	v[1]=2;
	v[2]=3;
	while(a<n){
		a++;
		while(a%2==0||a%3==0){
			a++;
		}
		j++;
		v[j]=a;
	}
	a=0;
	b=j;
	while(v[b]>n){
		b--;
	}
	for(i=1;i<=b;i++){
		if(v[i]>0){
			a++;
			for(j=i+1;j<=b;j++){
				if(v[j]%v[i]==0){
					v[j]=-1;
				}
			}
		}			
	}
	fprintf(f2,"%ld",a);
	return 0;
}