#include <cstdio>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <iomanip>

#define NMax 2000005
#define INF 0x3f3f3f3f
using namespace std;
int n,ANS;
bool p[NMax];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    p[2] = 0;
    ANS ++;
    for(int i = 3; i <= n; i += 2){
        if(p[i] == 0){
            ANS++;
            for(int j = i + i; j <= n; j += i){
                p[j] = 1;
            }
        }
    }
    printf("%d ",ANS);
    return 0;
}