ll@n,i,j;
char d[n+1]{};
d[1]=2;
rep(i,2,n+1){
	if(d[i]==0){
		rep(j,i,n+1,i){
			d[j]+=1;
		}
		rep(j,i*i,n+1,i*i){
			d[j]=-128;
		}
	}
}
wt(sum[i,1,n+1](d[i]<0?0:d[i]&1?-1:1));