#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <tuple>
#include <iomanip>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vec;
typedef vector<vec> mat;
#define rep(i, n) for(ll i = 0; i < (n); i++)
#define revrep(i, n) for(ll i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
/*
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll max3(ll a, ll b, ll c){return max(a, max(b, c));};
ll min3(ll a, ll b, ll c){return min(a, min(b, c));};
ll max4(ll a, ll b, ll c, ll d){return max(max(a, b), min(c, d));};
ll min4(ll a, ll b, ll c, ll d){return min(min(a, b), min(c, d));};
ll max5(ll a, ll b, ll c, ll d, ll e){return max(max(a, b), max3(c, d, e));};
ll min5(ll a, ll b, ll c, ll d, ll e){return min(min(a, b), min3(c, d, e));};
*/
const ll INFL = 1LL << 60;//10^18 = 2^60
const int INF = 1 << 30;//10^9
ll MOD = 1000000007;
//ll MOD = 998244353;

vector<ll> dy = {0, 0, 1, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, -1, 0, 0, 1, -1, 1, -1, 0};


ll pow_long(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2) res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}
ll pow_mod(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2){
      res *= x; res %= MOD;
    }
    x *= x; x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x){return pow_mod(x, MOD - 2);};

ll gcd(ll a, ll b){
    if(b == 0) return a;
    return gcd(b, a % b);
}

ll lcm(ll x, ll y){return x / gcd(x, y) * y;};

ll kai_mod(ll x){
  if(x == 0) return 1;
  return x * kai_mod(x-1) % MOD;
}


//コンビネーション
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
//facはn!,finvは1/n!
//invは逆元
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAXcomb; i++){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll comb(int n, int k){
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] % MOD * finv[n-k] % MOD;
}

const ll N_ = 1<<18;
ll seg[2 * N_ - 1];

void update(ll k, ll x){
  k += N_ - 1;
  seg[k] = x;
  while(k){
    k = (k-1) / 2;
    seg[k] = seg[2 * k + 1] + seg[2 * k + 2];
  }
}

ll get_sum(ll x, ll y, ll k, ll l, ll r){
  if(r <= x || y <= l) return 0;
  if(x <= l && r <= y) return seg[k];
  ll res = 0;
  res += get_sum(x, y, 2*k+1, l, (l+r)/2);
  res += get_sum(x, y, 2*k+2, (l+r)/2, r);
  return res;
}

ll solve(string S){
  ll sl = S.size();
  string ans = "";
  vector<ll> cnt(26, 0), used(26, 0);
  vector<ll> pos[26];

  rep(i, sl) cnt[S[i] - 'a']++;
  ll odd = 0;
  rep(i, 26) if(cnt[i] % 2) odd++;
  if(odd >= 2){
    return -1;
  }

  string ans1 = "", ans2 = "";
  rep(i, sl){
    used[S[i] - 'a']++;
    if(used[S[i] - 'a'] <= cnt[S[i] - 'a'] / 2) ans1 += S[i];
  }
  ans2 = ans1;
  reverse(ans2.begin(), ans2.end());
  ans += ans1;
  if(odd == 1){
    rep(i, 26) if(cnt[i] % 2) ans += 'a' + i;
  }
  ans += ans2;

  vector<set<ll>> s_pos(26);
  rep(i, 26) s_pos[i].clear();

  rep(i, sl){
    s_pos[S[i] - 'a'].insert(i);
  }

  rep(i, sl) update(i, 1);
  ll res = 0;
  rep(i, sl){
    ll at = *s_pos[ans[i] - 'a'].begin();
    res += get_sum(0, at, 0, 0, N_);
    update(at, 0);
    s_pos[ans[i] - 'a'].erase(at);
  }

  return res;

  ll cn = 0;
  rep(i, sl){
    char x = ans[i];
    ll plus = 0;
    rep(j, sl){
      if(S[j] == x){
        cn += plus;
        S[j] = 'A';
        break;
      }
      if(S[j] != 'A') plus++;
    }
  }
  return cn;
}

int main(){
  string tmpS;
  cin >> tmpS;
  cout << solve(tmpS) << endl;
}


Measured memory_bytes: 14084