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40 lines
837 B
C++
40 lines
837 B
C++
#include <iostream>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e6;
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int n, p, h_primes[N + 5], sum[N + 5];
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bool not_h_prime[N + 5], is_h_semi_prime[N + 5];
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int main() {
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std::ios::sync_with_stdio(false);
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for (int i = 5; i <= N; i += 4) {
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if (!not_h_prime[i]) {
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h_primes[++p] = i;
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for (int j = i * 5; j <= N; j += i * 4) {
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not_h_prime[j] = true;
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}
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}
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}
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for (int i = 1; i <= p; i++) {
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for (int j = 1; j <= i && h_primes[i] * h_primes[j] <= N; j++) {
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is_h_semi_prime[h_primes[i] * h_primes[j]] = true;
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}
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}
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for (int i = 1; i <= N; i++) {
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sum[i] = sum[i - 1] + is_h_semi_prime[i];
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}
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while (cin >> n, n) {
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cout << n << ' ' << sum[n] << endl;
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}
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return 0;
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}
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