#include<stdio.h>   
#define NMAX 32000//000
  
int main(){

freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);

int vprim[NMAX+1]={1,1},vsume[NMAX+1];

long long i,j,n;

scanf("%lld\n",&n);

for(i=2;i<=n;i++){
        if(vprim[i]==0)   
            for(j=2;j*i<=n;j++)   
                vprim[j*i]=1;   
}   
  
vsume[0]=0;   
for(i=1;i<=n;i++){   
    if(vprim[i]==0)   
        vsume[i]=vsume[i-1]+1;   
    else vsume[i]=vsume[i-1];   
}   
  
printf("%d\n",vsume[n]);   
return 0;   
}