#include <Servo.h>
Servo servo;  

int potpin = A0;  
int val;    
int angle=0;

void setup() {
  Serial.begin(9600);
  Serial.println("Enter angle (0 to 180):");
  
  servo.attach(9);  
}

void loop() {
  val = analogRead(potpin);            
  val = map(val, 0, 1023, 0, angle);     
  servo.write(val);
  delay(15);     
   

  if (Serial.available() > 0 ) { 
    String inputString = Serial.readStringUntil('\n');  
     angle = inputString.toInt();
     Serial.println(angle);
  }else if(angle<0 || angle>180){
    angle=0;
    Serial.println("Invalid input.Enter angles 0 to 180");
    }
  }