#include <stdio.h>
#define LL long long

LL i, j, sum, n;
LL phi[1000010];

int main() {
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    
    scanf("%lld",&n);
    
    for (i = 1; 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];
        sum += phi[i];
    }
    sum = sum * 2 + 1;
    
    printf("%lld\n",sum);
    
    return 0;
}