int n,m;
void setup()
 {
   pinMode(2,OUTPUT);
   n = 0;
   m = 0;
 }
void loop()
 
{
  if(n<25)
  {
   digitalWrite (2,1);
   delay (0+m) ;
   digitalWrite (2,0);
   delay (20-m) ;
  }
  else
  {
     delay (500) ;
     n=0;
     m=m+1;
     if(m>20)
       m=0;
  }
     n = n+1;
     
  
}