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  25T1020086  commented on Oct. 7, 2025, 8:32 a.m.

  include <bits/stdc++.h>

  using namespace std;

  int main() {

  double pi = 3.141592653;
  double r;
  cin >> r;
  cout << fixed << setprecision(9) << pi * (r*r);
  
  return 0;

  }

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