#include <cstdio>
#include <cmath>
int c[2000005];
int main(){
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int n,k=1,i,i2;
	scanf("%d ",&n);
	for( i=2 ; i<=n ; i+=2 )
		c[i]=1;
	for(i=3 ; i<=sqrt(n) ; i+=2 ){
		if( !c[i] ){ //daca c[i] nu e prim
			for( i2 = i+i ; i2<=n; i2+=i )
				c[i2]=1;
		}
	}
	for( i=3 ; i<=n; ++i )
		if(!c[i]) ++k;
	printf("%d ",k);
}