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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int main() {
  5.  
  6. // INPUT
  7. int r;
  8. cin >> r;
  9. // ALGORITHM
  10. double A = r * r * 3.14;
  11. // OUTPUT
  12. cout << A << endl;
  13.  
  14. return 0;
  15. }
Success #stdin #stdout 0.01s 5288KB
stdin
12
stdout
452.16