void Person::print_stamps() {
     char stamps_f[10];
     
     int x=0;
     for(int i=0;i<sizeof(stamps)-1;i++) {
             if(stamps[i] != '0') {
                          //x++;
                          stamps_f[x] = stamps[i];        
                          printf("[%c:%d]\n", stamps[i], x);
                          x++;
             }
     }
     
     printf("[system] %s has stamps: %s\n", name, stamps_f);
}