#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
#define N 100005

int s[N];
int prime[N],cntp;
bool isNot[N];

void getPrime()
{
    for(int i=2;i<=N;i++)
    {
        if(isNot[i]==0)
        {
            prime[cntp++]=i;
            for(int j=2;i*j<=N;j++)
                isNot[i*j]=1;
        }
    }
}
int lowbit(int x)
{
    return x&(-x);
}

void add(int x,int num)
{
    while(x<=N)
    {
        s[x]+=num;
        x+=lowbit(x);
    }
}

int sum(int x)
{
    int res=0;
    while(x>0)
    {
        res+=s[x];
        x-=lowbit(x);
    }
    return res;
}

int main()
{
    cntp=1;
    getPrime();
    for(int i=2;i<cntp;i++)
        if(prime[i]-prime[i-1]==2)
            add(prime[i],1);
    int n;
    while(scanf("%d",&n)!=EOF&&n>0)
    {
        printf("%d\n",sum(n));
    }
    return 0;
}