#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int buttonPin = 2;
unsigned long lastDebounceTime = 0;
unsigned long debounceDelay = 50;
int lastButtonState = HIGH;
int buttonState;

unsigned long long fibonacci(int n) {
  if (n <= 1) return n;
  unsigned long long a = 0, b = 1, c;
  for (int i = 2; i <= n; i++) {
    c = a + b;
    a = b;
    b = c;
  }
  return b;
}

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  lcd.init();
  lcd.backlight();

  randomSeed(analogRead(0));

  lcd.setCursor(0, 0);
  lcd.print("Press button");
}

void loop() {
  buttonState = digitalRead(buttonPin);

  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (buttonState == LOW) {  
      lastDebounceTime = millis();

      int randomNum = random(5, 31);

      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Num: ");
      lcd.print(randomNum);

      unsigned long startTime = micros();
      unsigned long long result = fibonacci(randomNum);
      unsigned long endTime = micros();

      float duration = (endTime - startTime) / 1000000.0;

      lcd.setCursor(0, 1);
      lcd.print("Time: ");
      lcd.print(duration, 5);
      lcd.print(" sec");

      char buffer[21];  
      sprintf(buffer, "%lu", (unsigned long)result);  
      lcd.setCursor(0, 2);
      lcd.print("Fib: ");
      lcd.print(buffer);
    }
  }
}