public int[] deletedPersonsIndices(){
        if(!this.dataPreprocessed)this.preprocessData();
        if(this.nDeletedPersons==0){
            System.out.println("Method - deletedPersonsIndices: there are no deleted persons; null returned");
            return null;
        }
        else{
            ArrayMaths am1 = new ArrayMaths(this.deletedPersonsIndices);
            ArrayMaths am2 = am1.plus(1);
            return am2.array_as_int();
        }
    }