using static System.Console;
using static System.Math;
 
public class Program {
    public static void Main() {
        if (double.TryParse(ReadLine(), out var raio)) WriteLine($"A = {PI * Pow(raio, 2):N4}");
	}
}
 
//https://pt.stackoverflow.com/q/286350/101
				dXNpbmcgc3RhdGljIFN5c3RlbS5Db25zb2xlOwp1c2luZyBzdGF0aWMgU3lzdGVtLk1hdGg7CgpwdWJsaWMgY2xhc3MgUHJvZ3JhbSB7CiAgICBwdWJsaWMgc3RhdGljIHZvaWQgTWFpbigpIHsKICAgICAgICBpZiAoZG91YmxlLlRyeVBhcnNlKFJlYWRMaW5lKCksIG91dCB2YXIgcmFpbykpIFdyaXRlTGluZSgkIkEgPSB7UEkgKiBQb3cocmFpbywgMik6TjR9Iik7Cgl9Cn0KCi8vaHR0cHM6Ly9wdC5zdGFja292ZXJmbG93LmNvbS9xLzI4NjM1MC8xMDE=