#include "bits/stdc++.h"
using namespace std;
const int MOD = 1e9 + 7;
typedef long long lint;
const int INF =1e7;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repi(i, k, n) for (int i = (k); i < (int)(n); ++i)
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define N 1000000
vi s(N + 1, 1);
void eli(int p)
{
    for (int i = p + p; i <= N; i = i + p)
    {
        s[i] = 0;
    }
}
void eratos(){
    s[0] = s[1] = 0;
    rep(i, N + 1)
    {
        if (s[i] == 1)
        {
            eli(i);
        }
    }
}
int main(){
    eratos();
    vi sum(N + 1, 0);
    rep(i,N){
        sum[i + 1] = sum[i] + s[i + 1];
    }
    int n;
    while(cin>>n){
        cout << sum[n] << endl;
    }

    return 0;
}
