Char-print

/*
LANG: C++
TASK: charprint
*/
#include<bits/stdc++.h>
using namespace std;

typedef long long int ll;

int const N = 300010;
ll fenwicktree[N];

void update(ll x){
    for(int i = x ; i <= N ; i += (i&-i)){
        fenwicktree[i]++;
    }
}

ll query(ll x){
    ll sum = 0;
    for(int i = x ; i >= 1 ; i -= (i&-i)){
        sum += fenwicktree[i];
    }
    return sum;
}


int main()
{
    int mode;
    scanf("%d",&mode);
    char field[N];
    char key[100010];
    scanf(" %s",field);
    scanf(" %s",key);

    deque<ll> allchar[260];
    for(ll i = 0 ; field[i] != '\0'; i ++)
        allchar[field[i]-'a'].push_back(i);


    ll cost = 0;
    if(mode == 0){
        for(int i = 0 ; key[i] != '\0' ; i ++){
            char kc = key[i];
            if(allchar[kc-'a'].size() > 0){
            //  printf("At %c Test cost : %d = %d + %d\n",kc,cost + allchar[kc-'a'][0],cost,allchar[kc-'a'][0]);
                cost += allchar[kc-'a'][0]+1;
                allchar[kc-'a'].pop_front();
            }
            else{
                printf("-1");
                return 0;
            }
        }
    }
    else {
        for(int i = 0 ; key[i] != '\0' ; i ++){
            char kc = key[i];
            if(allchar[kc-'a'].size() > 0){
            //  printf("Char %c at %d Test cost : %d = %d + (%d - %d)\n",kc,allchar[kc-'a'][0],cost + allchar[kc-'a'][0]+1 - query(allchar[kc-'a'][0]),cost,allchar[kc-'a'][0]+1,query(allchar[kc-'a'][0]));
                cost += allchar[kc-'a'][0]+1 - query(allchar[kc-'a'][0]);
                update(allchar[kc-'a'][0]+1);
                allchar[kc-'a'].pop_front();

            //  printf("Test query : ");for(int j = 0 ; j <= 20 ; j ++)printf("%d ",query(j));printf("\n");
            }
            else{
                printf("-1");
                return 0;
            }
        }
    }
    printf("%lld",cost);
    return 0;
}