int a=13;
int b=12;
int c=11;
int d=10;
int e=9;
int f=8;
int g=7;

void setup()
{pinMode (a, OUTPUT);
pinMode (b, OUTPUT);
pinMode (c, OUTPUT);
pinMode (d, OUTPUT);
pinMode (e, OUTPUT);
pinMode (f, OUTPUT);
pinMode (g, OUTPUT);}

void loop()
{digitalWrite (a,0);
digitalWrite (b,0);
digitalWrite (c,0);
digitalWrite (d,0);
digitalWrite (e,0);
digitalWrite (f,0);
digitalWrite (g,1);
delay (500);

digitalWrite (a,0);
digitalWrite (b,0);
digitalWrite (c,0);
digitalWrite (d,1);
digitalWrite (e,1);
digitalWrite (f,1);
digitalWrite (g,1);
delay (500);}