#include<stdio.h>
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
long long int n,i,j,k=0,v[1000001];
int main()
{
fscanf(f,"%lld",&n);
for(i=1;i<=n;i++) v[i]=i;
for(i=2;i<=n;i++) if(v[i]==i) for(j=i;j<=n;j+=i) v[j]=v[j]*(i-1)/i;
for(i=2;i<=n;i++) k+=v[i];
fprintf(g,"%lld",2*k+1);
return 0;
}