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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. const int MAXA = 1000000;
  4. vector<bool> isPrime(MAXA + 1, true);
  5. void sieve() {
  6.     isPrime[0] = isPrime[1] = false;
  7.     for (int i = 2; 1LL * i * i <= MAXA; i++) {
  8.         if (isPrime[i]) {
  9.             for (int j = i * i; j <= MAXA; j += i) {
  10.                 isPrime[j] = false;
  11.             }
  12.         }
  13.     }
  14. }
  15. int main() {
  16.     ios::sync_with_stdio(false);
  17.     cin.tie(nullptr);
  18.     sieve();
  19.     int n;
  20.     cin >> n;
  21.     long long ans = 0;
  22.     for (int i = 0; i < n; i++) {
  23.         for (int j = 0; j < n; j++) {
  24.             int x;
  25.             cin >> x;
  26.             if ((i == j || i + j == n - 1) && isPrime[x]) {
  27.                 ans++;
  28.             }
  29.         }
  30.     }
  31.  
  32.     cout << ans;
  33.     return 0;
  34. }
  35.  
Success #stdin #stdout 0.01s 5324KB
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https://ideone.com/Oy3rV0
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
secret

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