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  1. #include <iostream>
  2. #include <cmath>
  3. using namespace std;
  4.  
  5. int main()
  6. {
  7. double m,R;
  8. cin >> m >> R;
  9. cout << 2*R*sin(M_PI/m)*m;
  10. return 0;
  11. }
Success #stdin #stdout 0s 3464KB
stdin
27 20
stdout
125.38