String msg = "What is the radius of your circle:";
String msg2 = "Your circle area is: ";
int delayTime = 500;
float area;
float radius;
float pi = 3.14;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
Serial.println(msg);
while (Serial.available() == 0){
}
radius = Serial.parseFloat();
area = pi*radius*radius;
Serial.print(msg2);
Serial.println(area);
}