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31 lines
686 B
31 lines
686 B
#include <bits/stdc++.h>
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using namespace std;
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//判断是不是质数
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bool isPrime(int n) { //最快的方法
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if (n < 2) return false;
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if (n == 2 || n == 3) return true;
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if (n % 6 != 1 && n % 6 != 5) return false;
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for (int i = 5; i <= floor(sqrt(n)); i += 6)
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if (n % i == 0 || n % (i + 2) == 0)
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return false;
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return true;
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}
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int main() {
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int n;
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cin >> n;
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for (int i = 11; i <= n; ++i) {
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int shi, ge;
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shi = i / 10;
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ge = i % 10;
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int jingxiang = ge * 10 + shi;
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if (isPrime(i) && isPrime(jingxiang)) {
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cout << i << endl;
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}
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}
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return 0;
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}
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