#include<stdio.h>
int  n,i,j;
long long v[1001000],nr;
int main( void )
{

FILE * in = fopen("fractii.in", "r");
fscanf(in, "%d", &n);
fclose(in);
for(i = 2;i <= n;i++)
    v[i] = i - 1;
for(i = 2;i <= n;i++)
    for(j= i + i;j <= n;j += i)
        v[j] -= v[i];
for(i = 2;i <= n; i++)
    nr += v[i];
nr = 2 * nr + 1;
FILE * out = fopen("fractii.out", "w");
fprintf(out, "%lld", nr);
fclose(out);
return 0;
}