#include <Servo.h>

Servo servo [ 3 ];

void setup ()
{
  for ( byte n = 0; n < 3; n ++ )
  {
    servo [ n ].attach ( 4 + n, 500, 2500 );
    servo [ n ]. write ( 0 );
  }
  delay ( 1000 );
}

void loop ()
{
  for ( byte n = 0; n < 3; n ++ )
  {
    for ( byte pos = 0; pos < 180; pos ++ )
    {
      servo [ n ]. write ( pos );
      delay ( 20 );
    }
    for ( byte pos = 0; pos < 180; pos ++ )
    {
      servo [ n ]. write ( 180 - pos );
      delay ( 20 );
    }
  }
  }