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#include <iostream>
#include <cstdio>
using namespace std;
#define maxn 1000000+5
int a[maxn];
int main()
{
    int ans=0;
    for(int i=2;i<maxn;i++)
    {
        if(!a[i])
        {
            ans++;
            for(int j=i;j<maxn;j+=i)
                a[j]=ans;
        }
    }
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        printf("%d\n",a[n]);
    }
    return 0;
}