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

const int N = 100001;

ll phi[100001], res[100001];
 
void solve(){
	int i, j;
	for(i = 0; i < N; i++)phi[i] = i;
	for(i = 1; i < N; i++){
		for(j = 2 * i; j < N; j += i){
			phi[j] -= phi[i];
		}
	}
	for(i = 1; i <= N; i++){
        for(j = i; j <= N; j += i ) {
            res[j] += ( i * phi[i] );
        }
    }
}

int main(){
	solve();
	ll n;
	scanf("%lld",&n);
	printf("%lld", (n*(res[n]+1))/2);
}