不知道为啥会 RE，写的线性筛，数论分块，求挑错。

# include <bits/stdc++.h>
#define int long long
using namespace std;
int N, cnt;
int phi[2000007], pri[2000007];
bool vis[2000007];
int euler_phi () {
	phi[1] = 1;
	for (int i = 2; i <= 1000000; ++ i) {
		if (!vis[i]) {
			pri[++ cnt] = i;
			phi[i] = i - 1;
		}
		for (int j = 1; j <= cnt && i * pri[j] <= 1000000; ++ j) {
			vis[i * pri[j]] = 1;
			if (i % pri[j] == 0) {
				phi[i * pri[j]] = pri[j] * phi[i];
				break;
			}
			else
				phi[i * pri[j]] = phi[i] * phi[pri[j]];
		}
	}
	for (int i = 1; i <= 1000000; ++ i)
		phi[i] += phi[i - 1];
}
signed main () {
	euler_phi ();
	while (cin >> N) {
		if (N == 0) return 0;
		long long res = 0;
		int l = 1;
		while (l <= N) {
			int r = N / (N / l);
			res += (phi[r] - phi[l - 1]) * (N / l) * (N / l);
			l = r + 1;
		}
		cout << (res - (N + 1) * N / 2) / 2 << "\n";
	}
}