#include <stdio.h>
long long S;
long n,i,j,phi[1000001];
int main()
{
    FILE *f1,*f2;
    f1=fopen("fractii.in","r");
    f2=fopen("fractii.out","w");
    fscanf(f1,"%lld",&n);
    S=(n*(n-1))/2;
    for(i=2;i<=n;i++)
        phi[i]=i-1;
    for(i=2;i<=n;i++)
        for(j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    for(i=2;i<=n;i++)S+=phi[i];
    fprintf(f2,"%lld",S);
}