#include <stdio.h>

FILE *c = fopen("fractii.in","r"),*s = fopen("fractii.out","w");
long long n,fractii,v[1000001];

int main()
{
    fscanf(c,"%d",&n);
    for(int i=1;i<=n;i++)
        v[i] = i;
    for(int i=2;i<=n;i++)
        if(v[i] == i)
            for(int h=i;h<=n;h=h+i)
                v[h] = v[h] / i * (i-1);
    for(int i=2;i<=n;i++)
        fractii += v[i];
    fprintf(s,"%d",fractii*2+1);
    return 0;
}