// Adder outputs
const int S0 = A0;
const int S1 = A1;
const int S2 = A2;
const int S3 = A3;
const int C4 = A4;

// Units 7447
const int unitsA = 3;
const int unitsB = 6;
const int unitsC = 5;
const int unitsD = 4;

// Tens 7447
const int tensA = 8;
const int tensB = 11;
const int tensC = 10;
const int tensD = 9;

void setup() {

  pinMode(S0, INPUT);
  pinMode(S1, INPUT);
  pinMode(S2, INPUT);
  pinMode(S3, INPUT);
  pinMode(C4, INPUT);

  pinMode(unitsA, OUTPUT);
  pinMode(unitsB, OUTPUT);
  pinMode(unitsC, OUTPUT);
  pinMode(unitsD, OUTPUT);

  pinMode(tensA, OUTPUT);
  pinMode(tensB, OUTPUT);
  pinMode(tensC, OUTPUT);
  pinMode(tensD, OUTPUT);
}

void loop() {

  // Read adder output bits
  int s0 = digitalRead(S0);
  int s1 = digitalRead(S1);
  int s2 = digitalRead(S2);
  int s3 = digitalRead(S3);
  int c4 = digitalRead(C4);

  // Convert 5-bit binary to decimal (0-30)
  int sum = (c4 << 4) |
            (s3 << 3) |
            (s2 << 2) |
            (s1 << 1) |
             s0;

  int tens = sum / 10;
  int units = sum % 10;

  // Units digit
  digitalWrite(unitsA, units & 1);
  digitalWrite(unitsB, (units >> 1) & 1);
  digitalWrite(unitsC, (units >> 2) & 1);
  digitalWrite(unitsD, (units >> 3) & 1);

  // Tens digit
  digitalWrite(tensA, tens & 1);
  digitalWrite(tensB, (tens >> 1) & 1);
  digitalWrite(tensC, (tens >> 2) & 1);
  digitalWrite(tensD, (tens >> 3) & 1);
}