David likes number of estimates with base "k" and not a multiple(a%2!=0) of the number of zeros at the end. Set system and the number of the order and print it

I need to optimi this algoritm:

class David{
private:
 int k;
public:
 David();
 David(int);

 int operator[] (int);
};

 David::David(){
 k=10;        
 };
 David::David(int k){
 this->k=k;           
 }

 int David::operator[] (int n){
    int q;
    int p;
    int i=1;
    for(int r=0;r<n;i++){
        q=0;
        p=i;
        for(;;){
           if(p%k)
               break;
           if(p==0)
               break;
           ++q;
           p/=k;
        }
        if(q%2){
           r++;
        }
     }
     return i-1;
 }