Turning Lock Puzzle

#include <Arduino.h>
#include <TM1637Display.h>

#define CLK 2
#define DIO 3

TM1637Display display(CLK, DIO);

void setup()
{
  pinMode(4, INPUT); // Button-1 for Digit in 1000 Place
  pinMode(5, INPUT); // Button-1 for Digit in 100 Place
  pinMode(6, INPUT); // Button-1 for Digit in 10 Place
  pinMode(7, INPUT); // Button-1 for Digit in 1 Place
  pinMode(9, OUTPUT);

  display.setBrightness(2);
  Serial.begin(9600);
}

long numb = 1234; //random(1000,9999);

int pres4 = 0;
int pres5 = 0;
int pres6 = 0;
int pres7 = 0;

int numb4 = 0;
int numb5 = 0;
int numb6 = 0;
int numb7 = 0;

void loop()
{
  display.showNumberDec(numb, true);
  delay(100);

  //breaking 4-digited number into individual digits
  numb4 = numb / 1000;
  numb5 = (numb / 100) % 10;
  numb6 = (numb / 10) % 10;
  numb7 = numb % 10;

  //When Button is pressed, there is an Increment in Digits (Self + Adjacent Neighbors).
  //Digits represent Dial 0,1,2,3,4,5,6,7,8,9,0 etc.
  //Special Case: Incrementing 9 by 1 leads to 10, therefore need to reduce the left neighbor by 1.
  
  pres4 = digitalRead(4);
  if (pres4 == 1) {
    numb = numb + 1100;	//Digit in 1000 place increment by 1
    if (numb5 == 9) {
      numb = numb - 1000;	//Digit in 100 place decrement by 1
    }
    pres4 = 0;
  }

  pres5 = digitalRead(5);
  if (pres5 == 1) {
    numb = numb + 1110;	//Digit in 100 place increment by 1
    pres5 = 0;
    if (numb5 == 9) {
      numb = numb - 1000;	//Digit in 100 place decrement by 1
    }
    if (numb6 == 9) {
      numb = numb - 100;	//Digit in 10 place decrement by 1
    }
  }

  pres6 = digitalRead(6);
  if (pres6 == 1) {
    numb = numb + 111;	//Digit in 10 place increment by 1
    pres6 = 0;
    if (numb6 == 9) {
      numb = numb - 100;	//Digit in 10 place decrement by 1
    }
    if (numb5 == 9) {
      numb = numb - 1000;	//Digit in 1000 place decrement by 1
    }
    if (numb7 == 9) {
      numb = numb - 10;	//Digit in 1 place decrement by 1
    }
  }

  pres7 = digitalRead(7);
  if (pres7 == 1) {
    numb = numb + 11;	//Digit in 1 place increment by 1
    pres7 = 0;
    if (numb7 == 9) {
      numb = numb - 10;	//Digit in 1 place decrement by 1
    }
    if (numb6 == 9) {
      numb = numb - 100;	//Digit in 10 place decrement by 1
    }
  }

  if (numb > 9999) {
    numb = numb - 10000 * (numb / 10000);
  }

  Serial.println(numb);
  //LED to Glow or Buzzer to Ring
  if (numb == 0) {
    digitalWrite(9, HIGH);
  }
  else {
    digitalWrite(9, LOW);
  }
}