int

int on =  13;
int S1 =  12;
int S2 =  11;
int S3 =  10;
int S4 =  9;
volatile int c = 0;
long T0 = 0 ;
int A=500;

void setup() {
  pinMode(S1,OUTPUT);
  pinMode(S2,OUTPUT);
  pinMode(S3,OUTPUT);
  pinMode(S4,OUTPUT);
  Serial.begin(9600);
  attachInterrupt( 0,inte, LOW);
}

void loop() {

digitalWrite(on,HIGH);
while(c==0)
{   digitalWrite(S1,HIGH);
      digitalWrite(S2,HIGH);
      digitalWrite(S3,HIGH);
      digitalWrite(S4,HIGH);
      delay(A);  
  }
while(c==1)
{     digitalWrite(S1,HIGH);
      digitalWrite(S2,LOW);
      digitalWrite(S3,LOW);
      digitalWrite(S4,LOW);
      delay(A/2);
      digitalWrite(S1,LOW);
      digitalWrite(S2,HIGH);
      digitalWrite(S3,LOW);
      digitalWrite(S4,LOW);
      delay(A/2);
      digitalWrite(S1,LOW);
      digitalWrite(S2,LOW);
      digitalWrite(S3,HIGH);
      digitalWrite(S4,LOW);
      delay(A/2);
      digitalWrite(S1,LOW);
      digitalWrite(S2,LOW);
      digitalWrite(S3,LOW);
      digitalWrite(S4,HIGH);
      delay(A/2);
  }
while(c==2)
{    digitalWrite(S1,HIGH);
      digitalWrite(S2,LOW);
      digitalWrite(S3,HIGH);
      digitalWrite(S4,LOW);
      delay(A);
      digitalWrite(S1,LOW);
      digitalWrite(S2,HIGH);
      digitalWrite(S3,LOW);
      digitalWrite(S4,HIGH);
      delay(A);
  }
while(c==3)
{     
      digitalWrite(S1,HIGH);
      digitalWrite(S2,LOW);
      digitalWrite(S3,LOW);
      digitalWrite(S4,HIGH);
      delay(A);
      digitalWrite(S1,LOW);
      digitalWrite(S2,HIGH);
      digitalWrite(S3,HIGH);
      digitalWrite(S4,LOW);
      delay(A);
  }
while(c==4)
{
      digitalWrite(S1,HIGH);
      digitalWrite(S2,HIGH);
      digitalWrite(S3,HIGH);
      digitalWrite(S4,HIGH);
      delay(A/2);  
      digitalWrite(S1,LOW);
      digitalWrite(S2,LOW);
      digitalWrite(S3,LOW);
      digitalWrite(S4,LOW);
      delay(A/2);  
  }


}
void inte()
{  if ( millis() > T0  + 250)
          {    
            if(c<4)
            c++;
            else
            c=0;
              T0 = millis();
          }
}