void getAvailableLetters(const char lettersGuessed[], char availableLetters[]){
    char abeceda[]="abcdefghijklmnopqrstuvwxyz";
    int d=0;
    for(int i=0;i<strlen(abeceda);i++){
        if(!strchr(lettersGuessed,abeceda[i])){
            availableLetters[d]=abeceda[i];
            d++;
        }
    }
}