#include <stdio.h>
long long phi[1000000],S,n,i,j;
FILE*f=fopen("fractii.in","r");
FILE*g=fopen("fractii.out","w");
int main()
{
    fscanf(f,"%lld",&n);
    for(i=2;i<=n;i++)
        phi[i]=i-1;
    for(i=2;i<=n/2;i++)
        for(j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    for(i=2;i<=n;i++) S+=phi[i];
    fprintf(g,"%lld",2*S+1);


    fclose(f);
    fclose(g);
    return 0;
}