#include <bits/stdc++.h>
using namespace std;

const int N = 1e8 + 5;

bool vis[N];
vector<int> prim;

void get_prime(int n){
    for (int i = 2; i <= n; i++){
        if (!vis[i]) {
            prim.push_back(i);
            for (long long j = 1ll * i * i; j <= n; j += i){
                vis[j] = 1;
            }
        }
    }
}
int main(){
    int n;
    cin >> n;
    get_prime(n);
    int cnt = (int)prim.size();
    cout << cnt;
    
    return 0;
}

bool vis[N];改为bool vis[N] = {1， 1}; 提交就报CE是什么原因？本地没问题