#include <stdio.h>

char d[2000005];
int erast(long long n)
{
int h,j,c;
c=0;
   for(h=2; h<=n; h++)
		if (!d[h]) {
			++c;
			for (j = h+h; j<=n; j+=h)
				d[j]=1;
		}
return c;

}
int main()
{

long long b,c,i,j,a;

FILE *fp;
fp=fopen("fractii.in","r");
fscanf(fp,"%lld",&a);
b=(a-1)*2;
for(i=a;i>=2;i--)
{
c=erast(i);
b=b+(c-1)*2;
}
FILE *fw;
fw=fopen("fractii.out","w");
fprintf(fw,"%lld",b+1);
fclose(fp);
fclose(fw);
}