int 11 = 2;
int 12 = 3;
int b = 4;
void setup() {
pinMode(11, OUTPUT);
pinMode(12, OUTPUT);
pinMode(b, INPUT_PULLUP);
}
void loop() {
while(digitalRead(b)){}
delay(500);
while(digitalRead(b))
digitalWrite(11, HIGH);
digitalWrite(12, LOW);
delay(400);
digitalWrite(11, LOW);
digitalWrite(12, HIGH);
delay(400);
}