#include<bits/stdc++.h>
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define ppb pop_back
#define mp make_pair
#define ri(x) scanf("%d",&(x))
#define ri2(x,y) scanf("%d %d",&(x),&(y))
#define ri3(x,y,z) scanf("%d %d %d",&(x),&(y),&(z))
#define rll(x) scanf("%lld",&(x))
#define rll2(x,y) scanf("%lld %lld",&(x),&(y))
#define rll3(x,y,z) scanf("%lld %lld %lld",&(x),&(y),&(z))
#define gc(x) ((x) = getchar())
using namespace::std;

const long double PI = acos(-1);
const long long MOD = 1000000000 +7;

typedef long long ll;
typedef pair<ll,ll> pll;
typedef pair<ll,pll> tll;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
typedef vector<pll> vpll;
typedef vector<tll> vtll;
typedef vector<string> vs;
typedef set<int> si;
typedef set<ii> sii;
typedef set<iii> siii;

ll gcd(ll a, ll b){ return b==0?a:gcd(b,a%b);}

ll add(ll a, ll b, ll m = MOD){ return (a%m + b%m+2*m)%m;}

ll mul(ll a, ll b, ll m = MOD){ return ((a%m+m)*(b%m+m))%m;}

ll pow_mod(ll a, ll b, ll m = MOD){
	ll res = 1LL;
	a = a%m;
	while(b){
		if(b&1) res = mul(res,a,m);
		b >>= 1;
		a = mul(a,a,m);
	}
	return res;
}

ll fastexp(ll a, ll b){
	ll res = 1LL;
	while(b){
		if(b&1) res = res*a;
		b >>= 1;
		a *= a;
	}
	return res;
}

int gcdExtendido(int a, int b, int *x, int *y){
	if(a == 0){
		*x = 0;
		*y = 1;
		return b;
	}
	int x1, y1;
	int gcd = gcdExtendido(b%a,a,&x1,&y1);

	*x = y1-(b/a)*x1;
	*y = x1;
	return gcd;
}

int modInverso(int a, int m){
	int x, y;
	int g = gcdExtendido(a,m,&x,&y);
	if(g!=1) return -1;
	else return (x%m + m)%m;
}

/****************************************
*************P*L*A*N*T*I*L*L*A************
*****************************************/

const int N = 1000000+5;

int n;
int phi[N];
ll ans[N];

void init(){
	phi[1] = 0;
	for(int i=2; i<N; i++){
		if(!phi[i]){
			phi[i] = i-1;
			for(int j=i<<1; j<N; j+=i){
				if(!phi[j]) phi[j] = j;
				phi[j] -= phi[j]/i;
			}
		}
	}
	for(int i=1; i<N; i++){
		for(int j=i<<1; j<N; j+=i){
			ans[j] += 1LL*i*phi[j/i];
		}
	}
	for(int i=2; i<N; i++){
		ans[i] += ans[i-1];
	}
}


int main(){
	init();
	while(ri(n)==1 and n){
		printf("%lld\n",ans[n]);
	}
	return 0;
}