#line 2 "/Users/kaage/Desktop/ProgrammingWorkspace/library/other/template.hpp"
#define _CRT_SECURE_NO_WARNINGS
#pragma target("avx2")
#pragma optimize("O3")
#pragma optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <string.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define all(V) V.begin(),V.end()
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
typedef std::pair<lint, lint> LP;
constexpr int INF = INT_MAX/2;
constexpr lint LINF = LLONG_MAX/2;
constexpr double eps = DBL_EPSILON;
constexpr double PI=3.141592653589793238462643383279;
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
template <class T, class U>
inline bool chmax(T& lhs, const U& rhs) {
	if (lhs < rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
template <class T, class U>
inline bool chmin(T& lhs, const U& rhs) {
	if (lhs > rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
inline lint gcd(lint a, lint b) {
	while (b) {
		lint c = a;
		a = b; b = c % b;
	}
	return a;
}
inline lint lcm(lint a, lint b) {
	return a / gcd(a, b) * b;
}
bool isprime(lint n) {
	if (n == 1)return false;
	for (int i = 2; i * i <= n; i++) {
		if (n % i == 0)return false;
	}
	return true;
}
template<typename T>
T mypow(T a, lint b) {
	T res(1);
	while(b){
		if(b&1)res*=a;
		a*=a;
		b>>=1;
	}
	return res;
}
lint modpow(lint a, lint b, lint m) {
	lint res(1);
	while(b){
		if(b&1){
			res*=a;res%=m;
		}
		a*=a;a%=m;
		b>>=1;
	}
	return res;
}
template<typename T>
void printArray(std::vector<T>& vec) {
	rep(i, vec.size()){
		std::cout << vec[i];
		std::cout<<(i==(int)vec.size()-1?"\n":" ");
	}
}
template<typename T>
void printArray(T l, T r) {
	T rprev = std::prev(r);
	for (T i = l; i != rprev; i++) {
		std::cout << *i << " ";
	}
	std::cout << *rprev << std::endl;
}
LP extGcd(lint a,lint b) {
	if(b==0)return {1,0};
	LP s=extGcd(b,a%b);
	std::swap(s.first,s.second);
	s.second-=a/b*s.first;
	return s;
}
LP ChineseRem(const lint& b1,const lint& m1,const lint& b2,const lint& m2) {
	LP sol=extGcd(m1,m2);
	lint p=sol.first,q=sol.second;
	lint tmp=(b2-b1)*p%m2;
	lint r=(b1+m1*tmp+m1*m2)%(m1*m2);
	return std::make_pair(r,m1*m2);
}
template<typename F>
inline constexpr decltype(auto) lambda_fix(F&& f){
	return [f=std::forward<F>(f)](auto&&... args){
		return f(f,std::forward<decltype(args)>(args)...);
	};
}
#line 3 "/Users/kaage/Desktop/ProgrammingWorkspace/library/data-structure/BIT.hpp"
class BIT {
	int n;
	std::vector<lint> bit;
public:
	BIT(unsigned int n) :n(n) {
		bit.resize(n + 1);
	}
	void add(int a, lint x) {
		while (a <= n) {
			bit[a] += x;
			a += a & -a;
		}
	}
	lint query(int a) {
		lint cnt = 0;
		while (a > 0) {
			cnt += bit[a];
			a -= a & -a;
		}
		return cnt;
	}
	void clear() {
		bit.assign(n + 1, 0);
	}
	unsigned int lower_bound(int x){
		int p=0,k=1;
		while(k*2<=n)k*=2;
		while(k>0){
			if(p+k<=n&&bit[p+k]<x){
				x-=bit[p+k];
				p+=k;
			}
			k/=2;
		}
		return p+1;
	}
	unsigned int upper_bound(int x){
		int p=0,k=1;
		while(k*2<=n)k*=2;
		while(k>0){
			if(p+k<=n&&bit[p+k]<=x){
				x-=bit[p+k];
				p+=k;
			}
			k/=2;
		}
		return p+1;
	}
};
#line 3 "main.cpp"
std::string s;
int a[26],num[100010];
std::vector<int> vec[26];
int main(){
	std::cin>>s;
	for(const char& i:s)a[i-'a']++;
	int cnt=0;
	rep(i,26){
		if(a[i]%2)cnt++;
	}
	if((cnt!=1&&s.size()%2)||(cnt!=0&&s.size()%2==0)){
		std::cout<<-1<<std::endl;
		return 0;
	}
	std::string t,r;
	lint ans=0;
	bool f=false;
	rep(i,s.size()){
		if(a[s[i]-'a']>=2){
			a[s[i]-'a']-=2;
			ans+=i-t.size();
			t+=s[i];
		}
		else{
			if(!f&&a[s[i]-'a']==1){
				ans+=r.size();
				f=true;
			}
			else r+=s[i];
		}
	}
	std::reverse(all(r));
	rep(i,t.size()){
		vec[t[i]-'a'].push_back(i);
	}
	rep(i,26){
		int now=0;
		rep(j,r.size()){
			if(now<vec[i].size()&&r[j]=='a'+i){
				num[j]=vec[i][now];
				now++;
			}
		}
	}
	BIT bit(r.size());
	rep(i,r.size()){
		ans+=bit.query(r.size())-bit.query(num[i]);
		bit.add(num[i]+1,1);
	}
	std::cout<<ans<<std::endl;
	return 0;
}

Measured memory_bytes: 5508