#include <iostream>
#include<iomanip>
using namespace std;
int main() {
double d;
cin >> d;
cout << fixed << showpoint << setprecision(4) << "A=" << d*d*3.14159 << endl;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgojaW5jbHVkZTxpb21hbmlwPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwppbnQgbWFpbigpIHsKCWRvdWJsZSBkOwoJY2luID4+IGQ7Cgljb3V0IDw8IGZpeGVkIDw8ICBzaG93cG9pbnQgPDwgc2V0cHJlY2lzaW9uKDQpIDw8ICJBPSIgPDwgZCpkKjMuMTQxNTkgPDwgZW5kbDsKCXJldHVybiAwOwp9