import java.util.Arrays;

public class Main {

  private static void solve() {
    char[] s = ns();
    int n = s.length;
    int[] cnt = new int[26];
    for (int i = 0; i < n; i++) {
      s[i] -= 'a';
      cnt[s[i]]++;
    }

    int c = -1;
    for (int i = 0; i < 26; i++) {
      if (cnt[i] % 2 == 1) {
        if (c >= 0 || n % 2 == 0) {
          System.out.println(-1);
          return;
        }
        c = i;
      }
    }

    int[][] b = new int[26][];
    for (int i = 0; i < 26; i++) {
      b[i] = new int[cnt[i]];
    }
    int[] ptr = new int[26];
    for (int i = 0; i < n; i++) {
      b[s[i]][ptr[s[i]]++] = i;
    }
    Arrays.fill(ptr, 0);

    int[] a = new int[n];
    int p = 0;
    for (int i = 0; i < n; i++) {
      if (s[i] == c && ptr[s[i]] == cnt[s[i]] / 2) {
        a[i] = n / 2;
        ptr[s[i]]++;
      } else if (ptr[s[i]] * 2 < cnt[s[i]]) {
        int j = b[s[i]][cnt[s[i]] - ptr[s[i]] - 1];
        a[i] = p;
        a[j] = n - p - 1;
        ptr[s[i]]++;
        p++;
      }
    }


    //System.err.println(Arrays.toString(a));
    long ret = bubbleCount(a, 0, n);
    System.out.println(ret);
  }

  public static long bubbleCount(int[] a, int l, int r) {
    if (r - l <= 1)
      return 0;
    int m = (l + r) / 2;
    long ret = bubbleCount(a, l, m) + bubbleCount(a, m, r);
    int[] temp = Arrays.copyOfRange(a, l, r);
    for (int p0 = 0, p1 = m - l, p = l; p < r;) {
      if (p0 == m - l) {
        a[p++] = temp[p1++];
      } else if (p1 == r - l) {
        a[p++] = temp[p0++];
      } else if (temp[p0] <= temp[p1]) {
        a[p++] = temp[p0++];
      } else {
        a[p++] = temp[p1++];
        ret += m - l - p0;
      }
    }
    return ret;
  }


  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}



Measured memory_bytes: 46860