#include <cstdio>
#include <unordered_map>
#define lint long long
#define MAX 0
 
lint phi[MAX];
std::unordered_map<int, lint> mp;
 
lint S(int x) {
	int i, j;
	if (x < MAX) return phi[x];
	if (mp.find(x) != mp.end()) return mp[x];
	lint ret = x * (x + 1LL) / 2;
	for (i = 2; i <= x; i = j+1) {
		j = x / (x / i);
		ret -= (j - i + 1) * S(x / i);
	}
	return mp[x] = ret;
}
 
int main()
{
	int N, i, j;
	scanf("%d", &N);
 
	for (i = 1; i < MAX; ++i) {
		phi[i] += i;
		for (j = 2; j*i < MAX; ++j) phi[j*i] -= phi[i];
		phi[i] += phi[i-1];
	}
 
	printf("%lld", S(N));
	return 0;
}

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