#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize(3)
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("sse3","sse2","sse")
#pragma GCC target("avx","sse4","sse4.1","sse4.2","ssse3")
#pragma GCC target("f16c")
#pragma GCC optimize("inline","fast-math","unroll-loops","no-stack-protector")
#pragma GCC diagnostic error "-fwhole-program"
#pragma GCC diagnostic error "-fcse-skip-blocks"
#pragma GCC diagnostic error "-funsafe-loop-optimizations"
#pragma GCC diagnostic error "-std=c++14"
#include "bits/stdc++.h"
//#include "ext/pb_ds/tree_policy.hpp"
//#include "ext/pb_ds/assoc_container.hpp"
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x,"r",stdin)
#define fw(x) freopen(x,"w",stdout)
#define iout(x) printf("%d\n",x)
#define lout(x) printf("%lld\n",x)
#define REP(x,l,u) for(ll x = l;x<u;x++)
#define RREP(x,l,u) for(ll x = l;x>=u;x--)
#define complete_unique(a) a.erase(unique(a.begin(),a.end()),a.end())
#define mst(x,a) memset(x,a,sizeof(x))
#define all(a) a.begin(),a.end()
#define PII pair<int,int>
#define PLL pair<ll,ll>
#define MP make_pair
#define sqr(x) ((x)*(x))
#define lowbit(x) (x&(-x))
#define lson (ind<<1)
#define rson (ind<<1|1)
#define se second
#define fi first
#define dbg(x) cerr<<#x<<" = "<<(x)<<endl;
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef  long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;
typedef vector<ll> VLL;
typedef vector<int> VI;
const int block_size = 320;
typedef complex<ll> point;
const ll mod = 1e9+7;
const ll inf = 1e9+7;
const ld eps = 1e-9;
const db PI = atan(1)*4;
template<typename T>
inline int sign(const T&a) {
    if(a<0)return -1;
    if(a>0)return 1;
    return 0;
}

template<typename T,typename S>inline bool upmin(T&a,const S&b){return a>b?a=b,1:0;}
template<typename T,typename S>inline bool upmax(T&a,const S&b){return a<b?a=b,1:0;}

template<typename T> inline void in(T &x) {
    x = 0;
    T f = 1;
    char ch = getchar();
    while (!isdigit(ch)) {
        if (ch == '-') f = -1;
        ch = getchar();
    }
    while (isdigit(ch))  {
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    x *= f;
}

ll twop(int x) {
    return 1LL<<x;
}

template<typename A,typename B > inline void in(A&x,B&y) {
    in(x);
    in(y);
}
template<typename A,typename B,typename C>inline void in(A&x,B&y,C&z) {
    in(x);
    in(y);
    in(z);
}
template<typename A,typename B,typename C,typename D> inline void in(A&x,B&y,C&z,D&d) {
    in(x);
    in(y);
    in(z);
    in(d);
}
ll gcd(ll a,ll b){return b==0?a:gcd(b,a%b);}
namespace SOLVE {
    void main(){
    }
}
template<int maxn,typename NUM>
struct BIT {
    NUM s[maxn];
    
    void init() {
        mst(s, 0);
    }
    BIT() {
        init();
    }
    
    void update(int a,NUM value) {
        a++;
        while(a<maxn) {
            s[a]+=value;
            a+=lowbit(a);
        }
    }
    
    NUM query(int a) {
        NUM ans = 0;
        a++;
        while(a) {
            ans+=s[a];
            a-=lowbit(a);
        }
        return ans;
    }
    NUM query(int a,int b) {
        if(b<a)return 0;
        return query(b)-query(a-1);
    }
};
BIT<200010,int>bit;

deque<int>q[26];
int main() {
#ifndef ONLINE_JUDGE
 //   fr("/Users/zhangqingchuan/Desktop/cp/cp/input.txt");
   // fw("/Users/zhangqingchuan/Desktop/cp/cp/output.txt");
#endif
    
    
    
    
    
    
    
    
    
    SOLVE::main();
    string s;cin>>s;
    int n = sz(s);
    ll ans = 0;
    s = " "+s;
    REP(i,1,n+1)q[s[i]-'a'].PB(i),bit.update(i, 1);
    REP(i,1,n+1){
        if(bit.query(i, i)){
            if(sz(q[s[i]-'a']) >= 2){
                int l = i,r = q[s[i]-'a'].back();
                q[s[i]-'a'].pop_back();
                q[s[i]-'a'].pop_front();
                ans += bit.query(r+1,n);
                ans += bit.query(1,l-1);
                bit.update(l, -1);
                bit.update(r, -1);
            }
        }
    }
    int cnt = 0;
    REP(i,0,26)cnt+=sz(q[i]);
    if(cnt>1){
        cout<<-1;
    }else{
        cout<<ans;
    }
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    return 0;
}


Measured memory_bytes: 2112