#define btnA 13
#define btnB 12
#define btnC 14
int del=50, n=0, chr=99;
const int segmentPinsNum[] = {19,21,17,5,18,22,23}; 
const int digitPins[] = {16,4,0}; 

const byte chrs[3][7] = { // 0-9
  {1, 1, 1, 0, 1, 1, 1}, // A
  {0, 0, 1, 1, 1, 1, 1}, // b
  {0, 0, 0, 1, 1, 0, 1} // c
};
const byte digits[10][7] = { // 0-9
  {1, 1, 1, 1, 1, 1, 0}, // 0
  {0, 1, 1, 0, 0, 0, 0}, // 1
  {1, 1, 0, 1, 1, 0, 1}, // 2
  {1, 1, 1, 1, 0, 0, 1}, // 3
  {0, 1, 1, 0, 0, 1, 1}, // 4
  {1, 0, 1, 1, 0, 1, 1}, // 5
  {1, 0, 1, 1, 1, 1, 1}, // 6
  {1, 1, 1, 0, 0, 0, 0}, // 7
  {1, 1, 1, 1, 1, 1, 1}, // 8
  {1, 1, 1, 1, 0, 1, 1}  // 9
};

void setup() {
  pinMode(btnA, INPUT);
  pinMode(btnB, INPUT);
  pinMode(btnC, INPUT);
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPinsNum[i], OUTPUT);
  }
  for (int i = 0; i < 3; i++) {
    pinMode(digitPins[i], OUTPUT);
  }
}

void loop() {
  if(digitalRead(btnA)){
    while(digitalRead(btnA)){}
    chr=0;n++;
  }
  if(digitalRead(btnB)){
    while(digitalRead(btnB)){}
    chr=1;n++;
  }
  if(digitalRead(btnC)){
    while(digitalRead(btnC)){}
    chr=2;n++;
  }
  if(n>99){n=0;}
  while (!(digitalRead(btnA) || digitalRead(btnB)|| digitalRead(btnC))) {
    displayNumber(n);
  }
}

void displayNumber(int number) {
  int tens = number / 10;
  int ones = number % 10;

  // Display tens digit
  displayDigit(tens);
  digitalWrite(digitPins[0], LOW);
  delay(del);
  digitalWrite(digitPins[0], HIGH);
  
  // Display ones digit
  displayDigit(ones);
  digitalWrite(digitPins[1], LOW);
  delay(del);
  digitalWrite(digitPins[1], HIGH);

  // Display letter digit
  displayChr(chr);
  digitalWrite(digitPins[2], LOW);
  delay(del);
  digitalWrite(digitPins[2], HIGH);}

void displayDigit(int digit) {
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPinsNum[i], digits[digit][i]);
  }
}
void displayChr(int digit) {
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPinsNum[i], chrs[digit][i]);
  }
}