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@@ -0,0 +1,29 @@
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+#include<bits/stdc++.h>
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+
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+using namespace std;
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+
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+bool prime(int n) {
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+ if (n == 2)return true;
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+ if (n % 2 == 0 || n < 2)return false;
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+ for (int c = 3; c * c <= n; c += 2)
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+ if (n % c == 0)return false;
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+ return true;
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+}
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+
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+int solve(int n) {
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+ int tot = 0;
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+ int p = n >> 1;
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+ if (p % 2 == 0)--p;
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+ for (; p >= 3; p -= 2)
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+ if (prime(p) && prime(n - p)) {
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+ ++tot;
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+ }
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+ return tot;
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+}
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+
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+int main() {
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+ for (int n; cin >> n;)
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+ cout << solve(n) << endl;
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+ return 0;
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+}
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+
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