/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
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*******************************************************************************/

#include <iostream>
#include <cmath>
using namespace std;
int n = 4;
int answer = 1;
bool k[2000000];
int main()
{
    cin >> n;
    short i = 0;
    short j = 0;
    for(i=2;i<=sqrt(n);i++){
        if(k[i]==false){
            for(j=2;j<=n/i;j++){
                if(k[i*j]==false){
                    k[i*j]=true;
                    answer++;
                }
            }
        }
    }
    answer = n - answer;
    cout<<answer;
    
    return 0;
}