int led = 9;
int btn = 4;
void setup() {
  // put your setup code here, to run once:
  pinMode(led, OUTPUT);
  pinMode(4, INPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  if(digitalRead(btn) == HIGH){
    digitalWrite(led, HIGH);
    delay(1000);
  }else
  {
    digitalWrite(led, LOW);
  }
}