#include<stdio.h>
#include<math.h>
int nr[1000002],prim[100000];
int main(){
	FILE*in=fopen("fractii.in","r");
	FILE*out=fopen("fractii.out","w");
	int n,i,j,pr,a;
	fscanf(in,"%d",&n);
	if(n==1){
		fprintf(out,"1\n");
		return 0;
	}
	if(n==2){
		fprintf(out,"3\n");
		return 0;
	}
	
	i=4;
	while(i<=n){
		nr[i]=1;
		i=i+2;
	}
	for(i=3;i<=n+10;i=i+2){
		pr=1;
		if(nr[i]==0){
			for(j=3;((j*j<=i)&&(pr));j=j+2){
				if(i%j==0)
					pr=0;
			}
			if(pr){
				j=i+i;
				while(j<=n){
					nr[j]=1;
					j=j+i;
				}
			}
		}
	}
	
	prim[0]=2;
	j=1;
	for(i=3;i<=n+10;i=i+2){
		if(nr[i]==0){
			prim[j]=i;
			j++;
		}
	}
	i=0;
	
	long long s;
	if(n%2==0)
		s=n+n/2;
	if(n%2==1)
		s=n+n/2+1;
	
	
	for(i=3;i<=n;i++){
		for(j=0;j<=n;j++)
			nr[j]=0;
		pr=1;
		j=0;
		while(prim[j]<i){
			if(i%prim[j]==0){
				a=prim[j];
				while(a<=n){
					nr[a]=1;
					a=a+prim[j];
				}
				pr=0;
			}
			j++;
		}
		if(pr==1)
			s=s+n-(n/prim[j]);
		else{
			for(a=1;a<=n;a++){
				if(nr[a]==0)
					s++;
			}
		}
	}
	fprintf(out,"%d\n",s);
	
	fclose(in);
	fclose(out);
	return 0;
}