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


int main(){
    int N;
    cin>>N;
    vector<int> squirrel(N+1,0);
    for(int i=1;i<=N;i++){
        if(squirrel[i]==0){
            int pointer=i;
            int j=1;
            while(pointer*j*j<=N){
                squirrel[pointer*j*j]=i;
                j++;
            }
        }
    }
    int ans=0;
    for(int i=1;i<=N;i++){
        int j=N/squirrel[i];
        int k=(int)sqrt((double)j);
        ans+=k;
    }
    cout<<ans<<endl;
}