include[HTML_REMOVED]

define int long long

using namespace std;
const int N = 1e6+10;
int a[N];
bool st[N];
int prime[N];
int cnt=0;
int n,i,j;
signed main()
{
int n;
cin>>n;
for(i=2;i<=n;i)
{
if(!st[i])
{
prime[cnt]=i;
}
for(j=0;prime[j]<=n/i;j++)
{
st[i*prime[j]]=true;
if(i%prime[j]==0)
{
break;
}
}
}
cout<<(cnt);
return 0;

}