#include<stdio.h>

const int N = 1000005;

int e[N];
int sol = 0;

void euler(int n)
{
    for(int i=1;i<n;i++)
        e[i] = i;
    for(int i=2;i<n;i++) {
        if(e[i] == i)
            for(int j=i;j<n;j+=i)
                e[j] = e[j]/i * (i-1);
        sol+=2*e[i];
    }
}

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);

    int n;

    scanf("%d", &n);

    euler(n);

    printf("%d\n", sol+1);

    return 0;
}