#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);i++)
#define loop(i,x,n) for(int i=(x);i<(n);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define fir first
#define sec second
#define ub upper_bound
#define lb lower_bound
#define int long long
using namespace std;
const int MOD=1000000007;
const int INF=1000000009;

bool Is_Prime(int n){
  if(n==1) return false;
  for(int i=2;i*i<=n;i++){
    if(n%i==0){
      return false;
    }
  }
  return true;
}
int p[100006];

signed main(){
  loop(i,2,100001){
    if(Is_Prime(i))p[i]=1;
  }
  rep(i,100001)p[i+1]+=p[i];
  int n;
  while(cin>>n){
    cout<<p[n]<<endl;
  }
  return 0;
}