#include <stdio.h>
#include <stdbool.h>
long long i,j,n,i1,i2,m=2,i11,i22,n1;
bool a[1000000000];

int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%li",&n);
    n=1000000;
    for(i=6;i<n;i+=6)
    {
        i1=i-1;
        i2=i+1;

           if(!a[i1])
            {
                m++;i11=i1*6;
                for(j=i1;j<=n;j+=i11)
                      a[j]=1;
                     for(j=i1*i1;j<=n;j+=i11)
                            a[j]=1;
            }
           if(!a[i2])
            {
                m++;i22=i2*6;
                for(j=i2;j<=n;j+=i22)
                      a[j]=1;
            }
    }
    printf("%li",m);
    return 0;
}