int led = 12;
int push_button = 26;
int button = 0;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(push_button, INPUT_PULLUP);
}

void loop() {
  button=digitalRead(push_button);
  if(button==LOW){
    digitalWrite(led, HIGH);
    delay(500);
  }
  else{
    digitalWrite(led, LOW);
  }

}