Bình luận

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  ToiNhoDuongThanhThao  đã bình luận lúc 9, Tháng 6, 2026, 3:25

  include <iostream>

  include <vector>

  using namespace std;

  const int MAXVAL = 10000000; bool isprime[MAX_VAL + 1];

  bool is_palindrome(int n) { int reversed = 0, original = n; while (n > 0) { reversed = reversed * 10 + n % 10; n /= 10; } return original == reversed; }

  int main() { iosbase::syncwith_stdio(false); cin.tie(NULL);

  for (int i = 2; i <= MAX_VAL; i++) {
      is_prime[i] = true;
  }
  for (int i = 2; i * i <= MAX_VAL; i++) {
      if (is_prime[i]) {
          for (int j = i * i; j <= MAX_VAL; j += i) {
              is_prime[j] = false;
          }
      }
  }
  
  vector&lt;long long> beautiful_squares;
  for (int i = 2; i <= MAX_VAL; i++) {
      if (is_prime[i] && is_palindrome(i)) {
          beautiful_squares.push_back((long long)i * i);
      }
  }
  
  long long a, b;
  if (cin >> a >> b) {
      int count = 0;
      for (long long sq : beautiful_squares) {
          if (sq >= a && sq <= b) {
              count++;
          }
      }
      cout << count << "\n";
  }
  
  return 0;
  

  }