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#include <iostream> //standard input-output stream
#include <iomanip> //input_output_manipulation
using namespace std;
int main(int argc, char const *argv[])
{
float R;
cin >> R;
float A = 3.14159 * R * R;
cout << "A=" << fixed << setprecision(4) << A << endl;
return 0;
}
// setprecision counts whole number >>> EX:: 34.1234 is equal setprecision(6)
// When the fixed keyword is used, the argument in the setprecision()
// function specifies the number of decimal places to be printed in the output.