int stepsTotal = 0;
    int pos = 1;
    int i;
    
    // Loop over array from end to start
    for ( i = a.length - 1; i >= 0 ; i-- ) {
      if (i % 2 == 1 ) {
        stepsTotal += a[i];
      } else {
        stepsTotal += (a[i] * 3);
      }
    }
    
    // The closest multiple of 10 <= stepsTotal
    int multipleOf10 = 10 * ( stepsTotal / 10 );
    
    // If necessary, adjust to the closest multiple of 10 >= stepsTotal
    if ( multipleOf10 != stepsTotal )
      multipleOf10 += 10;
    
    checkdigit = multipleOf10 - stepsTotal;