//set many funcs template
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdbool.h>
#define inf 1072114514
#define llinf 4154118101919364364
#define mod 1000000007
#define pi 3.1415926535897932384

int max(int a,int b){if(a>b){return a;}return b;}
int min(int a,int b){if(a<b){return a;}return b;}
int zt(int a,int b){return max(a,b)-min(a,b);}
int round(int a,int b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
int ceil(int a,int b){if(a%b==0){return a/b;}return (a/b)+1;}
int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}
int lcm(int a,int b){int c=gcd(a,b);a/=c;return a*b;}
int nCr(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
int fact(int a){int i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
int pow(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
long long llmax(long long a,long long b){if(a>b){return a;}return b;}
long long llmin(long long a,long long b){if(a<b){return a;}return b;}
long long llzt(long long a,long long b){return llmax(a,b)-llmin(a,b);}
long long llround(long long a,long long b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
long long llceil(long long a,long long b){if(a%b==0){return a/b;}return (a/b)+1;}
long long llgcd(long long a,long long b){long long c;while(b!=0){c=a%b;a=b;b=c;}return a;}
long long lllcm(long long a,long long b){long long c=llgcd(a,b);a/=c;return a*b;}
long long llnCr(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
long long llfact(long long a){long long i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
long long llpow(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
double dbmax(double a,double b){if(a>b){return a;}return b;}
double dbmin(double a,double b){if(a<b){return a;}return b;}
double dbzt(double a,double b){return dbmax(a,b)-dbmin(a,b);}
int sortfncsj(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int sortfnckj(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int llsortfncsj(const void *a,const void *b){if(*(long long *)a>*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int llsortfnckj(const void *a,const void *b){if(*(long long *)a<*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int dbsortfncsj(const void *a,const void *b){if(*(double *)a>*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int dbsortfnckj(const void *a,const void *b){if(*(double *)a<*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}

int bit[524288]={0},n=524287;
int sum(int i){
    int s=0;
    while(i>0){
        s+=bit[i];
        i-=i&(-i);
    }
    return s;
}
void add(int i,int x){
    while(i<=n){
        bit[i]+=x;
        i+=i&(-i);
    }
}

int main(void){
    int i,j,k,l,b[256]={0},fl=0,np=1;
    int mem[32][262144]={0};
    int memc[256]={0};
    int mjc[256]={0};
    int kca[262144];
    char s[262144];
    long long res=0;
    scanf("%s",s);
    l=strlen(s);
    for(i=0;i<l;i++){
        b[s[i]]++;
    }
    for(i='a';i<='z';i++){
        if(b[i]%2){fl++;}
    }
    if(fl>=2){printf("-1\n");return 0;}
    for(i=0;i<l;i++){
        mjc[s[i]-'a']++;
        //printf("%d %d %d\n",ceil(b[s[i]],2),mjc[s[i]-'a'],b[s[i]]);
        if(b[s[i]]%2==1 && ceil(b[s[i]],2)==mjc[s[i]-'a']){
            kca[i]=(l+1)/2;
        }
        else if(ceil(b[s[i]],2)>=mjc[s[i]-'a']){
            memc[s[i]]++;
            kca[i]=np;np++;
            mem[s[i]-'a'][memc[s[i]]]=l+1-kca[i];
        }
        else{
            //printf("a");
            kca[i]=mem[s[i]-'a'][memc[s[i]]];
            memc[s[i]]--;
        }
    }
    for(i=0;i<l;i++){
        //printf("[%d]",kca[i]);
        res+=i-sum(kca[i]);
        add(kca[i],1);
    }
    printf("%lld\n",res);
    return 0;
}


Measured memory_bytes: 34944