#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
int x;
int s;
int n;
LiquidCrystal_I2C lcd(0x27,20,4);
void setup(){
  lcd.init();                     
  lcd.backlight();
  pinMode(A0, INPUT);
  pinMode(2, INPUT_PULLUP);
}
void loop(){
  if (digitalRead(2) == 0) {
    n = 1 - n;
    delay(100);
  }
  s = map(analogRead(A0), 0, 1023, 20, 1);
    lcd.setCursor(x, 0);
    lcd.print("Hello, world");
  if (n == 0) {
    x++;
    if (x > 8) {
    x = 0;
    }
  }
  else{
    x--;
    if (x < 0) {
    x = 8;
    }
  }
  delay(50 * s);
  lcd.clear();
}