import java.io.*;
import java.util.*;

public class Main {
  private static int ALPHABET_SIZE = 26;

  private static long solve(char[] cs) {
    List<Deque<Integer>> dequeList = new ArrayList<>();
    for (int i = 0; i < ALPHABET_SIZE; i++) {
      dequeList.add(new ArrayDeque<>());
    }
    for (int i = 0; i < cs.length; i++) {
      dequeList.get(cs[i] - 'a').add(i);
    }

    int numOddQueueCount = 0;
    for (Deque<Integer> deque : dequeList) {
      if (deque.size() % 2 == 1) {
        numOddQueueCount++;
      }
    }
    if (numOddQueueCount > 1) {
      return -1;
    }

    int[] initialValues = new int[cs.length];
    for (int i = 0; i < cs.length; i++) {
      initialValues[i] = i;
    }
    UpdateRangeGetRangeSegmentTree segmentTree = new UpdateRangeGetRangeSegmentTree(initialValues);
    long answer = 0;
    for (int i = 0; i < cs.length / 2; i++) {
      int minCost = Integer.MAX_VALUE;
      int minCostIndex = -1;
      for (int j = 0; j < ALPHABET_SIZE; j++) {
        Deque<Integer> deque = dequeList.get(j);
        if (deque.size() < 2) {
          continue;
        }
        int leftIndex = segmentTree.get(deque.peekFirst());
        int rightIndex = segmentTree.get(deque.peekLast());
        int cost = Math.abs(leftIndex - i) + Math.abs(cs.length - 1 - i - rightIndex);
        if (minCost > cost) {
          minCost = cost;
          minCostIndex = j;
        }
      }
      answer += minCost;

      segmentTree.update(0, dequeList.get(minCostIndex).pollFirst(), 1);
      segmentTree.update(dequeList.get(minCostIndex).pollLast() + 1, cs.length, -1);
    }

    return answer;
  }

  private static void execute(ContestReader reader, ContestWriter out) {
    char[] cs = reader.nextCharArray();
    out.println(solve(cs));
  }
  
  public static void main(String[] args) {
    ContestReader reader = new ContestReader(System.in);
    ContestWriter out = new ContestWriter(System.out);
    execute(reader, out);
    out.flush();
  }
}

// Verify CODE FESTIVAL 2015 final D
// https://atcoder.jp/contests/code-festival-2015-final-open/tasks/codefestival_2015_final_d

class UpdateRangeGetRangeSegmentTree {
  private final int n;
  private final int[] lazies;
  private final int[] values;
  
  public UpdateRangeGetRangeSegmentTree(int[] initialValues) {
    int tempN = 1;
    while (tempN < initialValues.length) {
      tempN *= 2;
    }
    n = tempN;
    lazies = new int[2 * n - 1];
    values = new int[2 * n - 1];
    for (int i = 0; i < 2 * n - 1; i++) {
      lazies[i] = 0;
      values[i] = 0;
    }
    for (int i = 0; i < initialValues.length; i++) {
      values[i + n - 1] = initialValues[i];
    }
    for (int i = initialValues.length; i < n; i++) {
      values[i + n - 1] = 0;
    }
    for (int i = n - 2; i >= 0; i--) {
      values[i] = values[2 * i + 1] + values[2 * i + 2];
    }
  }
  
  private void eval(int k, int l, int r) {
    if (lazies[k] == 0) {
      return;
    }
    values[k] = values[k] + lazies[k];
    if (r - l > 1) {
      lazies[2 * k + 1] = lazies[2 * k + 1] + lazies[k];
      lazies[2 * k + 2] = lazies[2 * k + 2] + lazies[k];
    }
    lazies[k] = 0;
  }
  
  private void update(int a, int b, int lazy, int k, int l, int r) {
    eval(k, l, r);
    if (b <= l || r <= a) {
      return;
    }
    if (a <= l && r <= b) {
      lazies[k] = lazies[k] + lazy;
      eval(k, l, r);
    } else {
      update(a, b, lazy, 2 * k + 1, l, (l + r) / 2);
      update(a, b, lazy, 2 * k + 2, (l + r) / 2, r);
      values[k] = values[2 * k + 1] + values[2 * k + 2];
    }
  }
  
  public void update(int a, int b, int lazy) {
    update(a, b, lazy, 0, 0, n);
  }
  
  private int getRange(int a, int b, int k, int l, int r) {
    if (b <= l || r <= a) {
      return 0;
    }
    eval(k, l, r);
    if (a <= l && r <= b) {
      return values[k];
    }
    int vl = getRange(a, b, 2 * k + 1, l, (l + r) / 2);
    int vr = getRange(a, b, 2 * k + 2, (l + r) / 2, r);
    return vl + vr;
  }
  
  public int getRange(int a, int b) {
    return getRange(a, b, 0, 0, n);
  }
  
  public int get(int a) {
    return getRange(a, a + 1);
  }
/*
  private void dump(List list) {
    int sum = 0;
    for (int i = 0; sum + (1 << i) <= 2 * n - 1; sum += 1 << i, i++) {
      for (int j = sum; j < sum + (1 << i); j++) {
        System.err.print(list.get(j));
        System.err.print(" ");
      }
      System.err.println();
    }
    System.err.println();
  }
  
  public void dump() {
    System.err.println("values: ");
    dump(values);
    System.err.println("lazies: ");
    dump(lazies);
  }
  */
}

class ContestWriter extends PrintWriter {
  ContestWriter(PrintStream printeStream) {
    super(printeStream);
  }

  public void printList(List<? extends Object> list) {
    for (Object object : list) {
      println(object);
    }
  }

  public void printListOneLine(List<? extends Object> list) {
    List<String> stringList = new ArrayList<>();
    for (Object object : list) {
      stringList.add(object.toString());
    }
    println(String.join(" ", stringList));
  }
}

class ContestReader {
  private static final int BUFFER_SIZE = 1024;
  
  private final InputStream stream;
  private final byte[] buffer;
  private int pointer;
  private int bufferLength;
  
  ContestReader(InputStream stream) {
    this.stream = stream;
    this.buffer = new byte[BUFFER_SIZE];
    this.pointer = 0;
    this.bufferLength = 0;
  }
  
  private boolean hasNextByte() {
    if (pointer < bufferLength) {
      return true;
    }
    
    pointer = 0;
    try {
      bufferLength = stream.read(buffer);
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    return bufferLength > 0;
  }
  
  private int readByte() {
    if (hasNextByte()) {
      return buffer[pointer++];
    } else {
      return -1;
    }
  }
  
  private static boolean isPrintableChar(int c) {
    return 33 <= c && c <= 126;
  }
  
  public boolean hasNext() {
    while (hasNextByte() && !isPrintableChar(buffer[pointer])) {
      pointer++;
    }
    return hasNextByte();
  }
  
  public String next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    StringBuilder sb = new StringBuilder();
    while(true) {
      int b = readByte();
      if (!isPrintableChar(b)) {
        break;
      }
      sb.appendCodePoint(b);
    }
    return sb.toString();
  }
  
  public String nextLine() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    StringBuilder sb = new StringBuilder();
    while(true) {
      int b = readByte();
      if (!isPrintableChar(b) && b != 0x20) {
        break;
      }
      sb.appendCodePoint(b);
    }
    return sb.toString();
  }
  
  public char nextChar() {
    return next().charAt(0);
  }
  
  public int nextInt() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    
    int n = 0;
    boolean minus = false;
    
    {
      int b = readByte();
      if (b == '-') {
        minus = true;
      } else if ('0' <= b && b <= '9') {
        n = b - '0';
      } else {
        throw new NumberFormatException();
      }
    }
    
    while(true){
      int b = readByte();
      if ('0' <= b && b <= '9') {
        n *= 10;
        n += b - '0';
      } else if (b == -1 || !isPrintableChar(b)) {
        return minus ? -n : n;
      } else {
        throw new NumberFormatException();
      }
    }
  }
  
  public long nextLong() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    
    long n = 0;
    boolean minus = false;
    
    {
      int b = readByte();
      if (b == '-') {
        minus = true;
      } else if ('0' <= b && b <= '9') {
        n = b - '0';
      } else {
        throw new NumberFormatException();
      }
    }
    
    while(true){
      int b = readByte();
      if ('0' <= b && b <= '9') {
        n *= 10;
        n += b - '0';
      } else if (b == -1 || !isPrintableChar(b)) {
        return minus ? -n : n;
      } else {
        throw new NumberFormatException();
      }
    }
  }
  
  public double nextDouble() {
    return Double.parseDouble(next());
  }
  
  public String[] next(int n) {
    String[] array = new String[n];
    for (int i = 0; i < n; i++) {
      array[i] = next();
    }
    return array;
  }
  
  public String[] nextLine(int n) {
    String[] array = new String[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextLine();
    }
    return array;
  }
  
  public char[] nextChar(int n) {
    char[] array = new char[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextChar();
    }
    return array;
  }
  
  public int[] nextInt(int n) {
    int[] array = new int[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextInt();
    }
    return array;
  }
  
  public long[] nextLong(int n) {
    long[] array = new long[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextLong();
    }
    return array;
  }
  
  public double[] nextDouble(int n) {
    double[] array = new double[n];
    for (int i = 0; i < n; i++) {
      array[i] = nextDouble();
    }
    return array;
  }
  
  public char[] nextCharArray() {
    return next().toCharArray();
  }
  
  public String[][] next(int n, int m) {
    String[][] matrix = new String[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = next();
      }
    }
    return matrix;
  }
  
  public int[][] nextInt(int n, int m) {
    int[][] matrix = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextInt();
      }
    }
    return matrix;
  }
  
  public char[][] nextChar(int n, int m) {
    char[][] matrix = new char[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextChar();
      }
    }
    return matrix;
  }
  
  public long[][] nextLong(int n, int m) {
    long[][] matrix = new long[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextLong();
      }
    }
    return matrix;
  }
  
  public double[][] nextDouble(int n, int m) {
    double[][] matrix = new double[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        matrix[i][j] = nextDouble();
      }
    }
    return matrix;
  }
  
  public char[][] nextCharArray(int n) {
    char[][] matrix = new char[n][];
    for (int i = 0; i < n; i++) {
      matrix[i] = next().toCharArray();
    }
    return matrix;
  }
}


Measured memory_bytes: 39216