int led1= 9;
int led2 = 6;
int btn=4;
int rbtn;
void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(btn, INPUT);
}

void loop() {
  rbtn = digitalRead(btn);
  while(rbtn == HIGH){
    repetir();
  }
}
void repetir() {
  digitalWrite(led1, HIGH);  
  digitalWrite(led2, LOW);
  delay(1000);                   
  digitalWrite(led1, LOW);
  digitalWrite(led2, HIGH); 
  delay(1000);
}