#include <stdio.h>
#include <stdlib.h>
int phi[1000000];
long long s;
void euler(int n)
{
    int i,j;
    for (i=1;i<=n;i++)
        phi[i]=i-1;
    for (i=2; i<=n; i++)
    {
        s=s+phi[i];
        for (j=2*i; j<=n; j+=i)
            phi[j]-=phi[i];
    }
    printf("%lld",2*s+1);
}
int main()
{
    FILE *pf,*pg;
    pf=fopen("fractii.in","r");
    pg=fopen("fractii.out","w");
    unsigned int n;
    fscanf(pf,"%d",&n);
    euler(n);
    return 0;
}