#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  pinMode(4, OUTPUT);
  pinMode(7, INPUT);
  lcd.begin(16, 2);
  lcd.backlight();
  lcd.print("OK");
}

void loop() {
  lcd.clear();
  lcd.print(digitalRead(7));
  if(digitalRead(7)) {
    digitalWrite(4, HIGH);
  } else {
    digitalWrite(4, LOW);
  }
  delay(1);
}