#include <cstdio> 
#include <cmath> 
bool 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=3 ; i<=n ; i+=2 ){        
		if( !c[i] ){++k; //daca c[i] nu e prim           
			for( i2 = i+i ; i2<=n; i2+=i )                
				c[i2]=1;        
			}    
	}     
	printf("%d ",k); 
}