package chelper;

import io.InputReader;
import io.OutputWriter;

public class SnarkD {
  public void solve(int testNumber, InputReader in, OutputWriter out) {
    int n = in.nextInt();

    for (int i = 0; i < n; i++) {
      double l = in.nextInt() / 2.0;
      double r = in.nextInt();

      if (r < l) {
        out.println(Math.PI * r * r);
        continue;
      }

      if (r > l * Math.sqrt(2)) {
        out.println(4 * l * l);
        continue;
      }

      double a = Math.acos(1.0 * l / r);

      out.println((Math.PI - 4 * a) * r * r + l * Math.sin(a) * r * 4);
    }
  }
}