#include<bits/stdc++.h>
using namespace std;
int s[999999];
int qq(int n){
    int i,o=1;
    if(n<2){
        o=0;
    }
    else{
        for(i=2;i<=sqrt(n);i++){
            if(n%i==0){
                o=0;
                break;
            }
        }
    }
    return o;
}
int main(){
    int n=1,i,k=0;
    while(n!=0){
        cin>>n;
        for(i=1;i<=n;i++){
            if(qq(i)==1){
                s[k]++;
            }
        }
        k++;
    }
    for(i=0;i<k-1;i++){
        cout<<s[i]<<endl;
    }
    return 0;
}
/**************************************************************
	Problem: 1176
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:5980 kb
****************************************************************/