void setup() {
  // put your setup code here, to run once:
 pinMode(9, OUTPUT);
 pinMode(10, OUTPUT);
 pinMode(11, OUTPUT);
 pinMode(2, INPUT);
}
void red(){
 digitalWrite(11, HIGH);
 digitalWrite(10, LOW);
 digitalWrite(9, LOW);
 delay(1000);
}
void green(){
 digitalWrite(11, LOW);
 digitalWrite(10, HIGH);
 digitalWrite(9, LOW);
 delay(1000);
}
void yellow(){
 digitalWrite(11, HIGH);
 digitalWrite(10, HIGH);
 digitalWrite(19, LOW);
}
void loop() {
  // put your main code here, to run repeatedly:
 int state;
 state = digitalRead(2);
 if(0==state){
   red();
 }
 else if(1==state){
   green();
 }
}