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#include<cstdio>
int n,i,j,k;
char p[2000001];
int main()
{
freopen("ciur.in","r",stdin),freopen("ciur.out","w",stdout),scanf("%d",&n);
for(i=1;((i*i)<<1)+(i<<1)<=n;i++)
if(!(p[i>>3]&(1<<(i&7))))
for(j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
p[j>>3]|=(1<<(j&7));
for(i=1;2*i+1<=n;i++)
if(!(p[i>>3]&(1<<(i&7))))
k++;
printf("%d",k+1);
}