#include<cstdio>
    using namespace std;
    int n , v[1000000];
    long long nr;

    int main()
    {
        freopen("fractii.in" , "r" , stdin );
        freopen("fractii.out" , "w" , stdout );
        scanf("%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 j = i; j <= n ; j+=i)
                v[j] -= v[j]/i;
        for( int i = 1 ; i<= n ; ++i )
            nr+= v[i];
        nr = nr*2-1;
        printf("%lld" , nr);
        return 0;
    }