#include<iostream.h>
#include<fstream.h>
int main()
{long long n, b=0, i, j;
fstream f("ciur.in", ios::in);
fstream go("ciur.out", ios::out);

f>>n; 

for(i=n; i>=2; i--)
	{
		int g=0;
		for(j=2; (j<i)&&(g==0); j++)
		if((i%j)==0)
			g=1; 
		if(g==0)
			b++;
if(n%2!=0) i--;}

if(n%2!=0)
go<<b+1;
else go<<b;
}