#include<Servo.h>

Servo s1;


void setup() 
{
  s1.attach(9);
}

void loop() 
{

 for (int i=0; i<= 180; i+= 1)
   {
    s1.write(i);             
    delay(15);                     
   }
    
 for (int i=180; i>=0; i-= 1) 
   { 
    s1.write(i);            
    delay(15);                      
   }

}