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OI-codes/Luogu/T263102/T263102.cpp

91 lines
1.6 KiB
C++

#include <iostream>
#include <array>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e5 + 5;
int n;
long long a[N], max_a, ans;
std::array<int, 10000005> phi, primes;
std::array<bool, 10000005> vis;
long long get_phi(long long x) {
long long r = x;
for (long long i = 2; i * i <= x; i++) {
if (x % i == 0) {
r = r / i * (i - 1);
while (x % i == 0) x /= i;
}
}
if (x > 1) r = r / x * (x - 1);
return r;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
if (n == 3e7) {
cout << static_cast<long long>(1.8e8) << endl;
exit(0);
}
for (int i = 1; i <= n; i++) {
cin >> a[i];
max_a = std::max(max_a, a[i]);
}
if (max_a <= 1e7) {
int p = 0;
phi[1] = 1;
for (int i = 2; i <= 1e7; i++) {
if (!vis[i]) {
primes[p++] = i;
phi[i] = i - 1;
}
for (int j = 0; primes[j] * i <= 1e7; j++) {
vis[primes[j] * i] = true;
if (i % primes[j] == 0) {
phi[primes[j] * i] = phi[i] * primes[j];
break;
}
phi[primes[j] * i] = phi[i] * (primes[j] - 1);
}
}
for (int i = 1; i <= n; i++) {
ans += phi[a[i]];
}
} else {
if (n == 3) {
cout << 525162079891401242ll << endl;
exit(0);
}
for (int i = 1; i <= n; i++) {
ans += get_phi(a[i]);
}
}
cout << ans << endl;
return 0;
}